In the field of mechanical engineering, we have vast range of topics to select from. At present, companies and governments are dealing with two issues. First, is about global warming and other is about competition. For both these issues, mechanical engineers can contribute alot. For example, to improve the competitiveness of organization, you can build automation tools or robots which can help the company to improve its efficiency and similarly for global warming, you can bring some news ideas to either save energy or generate it without doing harm to the nature. The biggest positive about these are that solutions of both these issues are going to come from mechanical. This is the reason, I always recommend students to select topics which are related to either robotics or renewable energy. I myself tried to find all the latest topics from around the world and write about them to give you some more insight of what’s happening around. Robotics 
Robotics Projects Robotics would be a good choice in mechanical projects : Robots are very attractive in comparison to other projects and if everything goes well they will make you win.

Mechanical Projects related to Robotics

Though I  have written separate post about robotics here but as a starting point I would like to share all important links in this section. Using given links you can enhance your knowledge before building your own machines.

Solar Energy Projects 

Topics based on sun energy is one of my favorite in mechanical engineering because despite its easy to understand working and concept, work based on this energy is very useful and effective for our future energy needs.

Concept : Generally they work on this concept:

Solar Energy –> Solar Panel –> Electricity –> Machine(Grinder, Juicer, Mobile Charger, Bag etc.) or Storage(Battery)
Solar Energy–>Heat–>Cooking, Boiling, Water Filter etc .

Important thing to consider in your assignment is that how you can improve its efficiency either for boiling purpose or for heating. For ex.  Recently discussed Spherical cell concentrate more sun light at one place and therefore generates more power similarly scientist have found out that nano solar cells are more flexible and more efficient than any other cell available.

Solar Compressor:
You can build something which gets its power from Sun Energy. For e.g., power your AC of a small room using compressor which get its power from panels.Such as Solar Powered Air Conditioner
In this example, it is a small room. Half ton capacity will be sufficient. You will need at least kWh/24 hours. This may require 10 to 12 square meter panel plus battery and inverter.

Books on Solar Energy (pdf): 
Solar
Solar2

Hovercraft

Hovercraft definition by wiki : click here
It would be awesome if you design a hover car using tools of your house.

How to Build my own Hovercraft?

Engines 

Stirling Engine :

Mechanical engineering Stirling Engine Projects



Video and Complete Explanation of Stirling Engine

Stirling Engine Mini RC Car: We had discussed both Stirling Engine and Remote control cars in two separate posts. In this post we will combine these two technologies.

Sun Powered Stirling Engine Generator:

Windmill Projects:


We all know how we can generate electricity using windmills with the help of its revolution energy and turbines. I have tried to list out some other important stuff we can do using this energy. Though I have written independent article only on windmill projects but sky is the limit for what you can do with this energy. In my opinion, if anything which can produce rotational energy instantly is wind energy and mini projects can be build and tested using small room fan. With all these benefits, I will recommend you to give it a chance. In any mechanical projects science fair competition, you can give demonstration using fan.

Wind Mill Water Pump :
How to build wind mill pump?

Related links :
How to make model of Wind Mill?
Wind Mill Power Generation System
Wind turbine kites

Wind Powered Drip irrigation System
Wind Mill Pump

Remote Control Cars

Building Fast Remote Control Cars
RC Control Computer Cars

Related links :
Demolition RC Car
RCC
Hydrogen cell operated remote control car
Computer controlled car

Projects based on trains

Steam engines 
These engines are powered by steam and building them will help you to understand the concept and working of steam engines. Almost all mechanical engineers study about them in their introductory class of engines itself. Though steam engines are most ancient engines, but it is still one of the most widely used engine.Thermal power plants are one of such use.Nowadays, due to the problem of global warming, we should find a way to produce steam using renewable sources of energy.Couple of renewable steam engines, I discussed on this blog are Solar Powered steam engine and Solar Turbine Generator.
The most exciting thing about this engine is that we can still view its most raw form as stem engine powered trains.

Related:

Homemade Steam Engine
Steam engine powered bicycle

These engines are powered by steam and will help you to understand the concepts behind steam engines : Maglev Trains
Propeller Monorail

More :
3D Solar Cells  : Very Effective Design of solar cell. Used to enhance the efficiency of Solar Cell Significantly.

Hydraulic Car Lift : Its Details with fluid and how we can use it to lift the car.
Power Generation using Footsteps : Piezoelectric techniques used to convert energy of our footsteps in electricity.
Stair climbing Hand Cart : Handcart which would help you carry heavy materials upstairs.
Car Monitoring System
Highway Wind Turbines : Simple demonstration of how to use wind turbines at the divider of the road to generate electricity.
Power generation using Railway Tracks : See how we can use Variable capacitor for generating electricity. If implemented as expected, this is going to revolution in the field of renewable energy.
Stirling Engine Mini RC Car
Nitro Cars  : Cars powered by methane and nitro methane.
Fruit Picking Robot : Picking a fruit from garden is always a difficult task. Can you imagine how much easier it would become if Machines start to do this job for us? If yes , then this post will help you understanding its parts and mechanism.
Soccer Playing Mini robots : I have seen robots football championship of machines in many science fairs organized in colleges around the world where mechanical engineering graduates participate with their amazing machines.Though this is an old topic but I still consider it sharing to bring it in your notice.
Produce fuel using sun light  : Produce synthetic gas using CO2, oxygen and water.
Pedal Powered Water Filter: Filter water throughout the year ,day or noon using the simple concept of evaporation and condensation.
Pedal Powered Juicer Grinder
Light Weight Floating Wind Turbine : Whenever we think about wind turbine, first picture comes to our mind is of big farmland with large turbine. Light Weight turbine is completely opposite of that and not only that, it floats on water too.
Bio gas Powered Water Heater 
Bicycle Powered Cell Phone Charger : Have you thought about charging your cell phone using your cycle. This idea would discuss about all that.
Steam engine powered Bicycle : Whenever we thought about steam engines, the first thought comes to our mind is train engine,but have you ever thought of steam engine powered by cycle?
Mechanical Sprayer : Spray pesticides using human energy instead of fossil fuel or electricity.
Mechanical Creeper for Disable Person : This idea is one of my favorite because we never think of difficulties faced by differently abled people while working below the cars. This project will help understand his or her situation effectively.
Waste Management Machine
Water Powered Generator
Air Exchanger Ventilation System
Fuzzy logic approach for Traffic signals control of an isolated intersection( Report in PDF)
Synchromesh gear

Latest Projects:

Formula One Racing Car : Students of Amity University, Noida manufactured a car which can make anyone proud. It weights around 340 kg including driver and its top speed is 105km/hr.More Info

Protective Gloves: Another topic which I have seen recently is electric gloves which can be used by girls for their protection. They are easy to wear and protect the wearer by giving electric shock.

More :
CAD Project Ideas & Catia  (Design Engineers Topics)
Thermal Engineering Projects
HydroPower Topics 
Aeronautical Projects 
Design and Development of Smoke flow Visualization system
Tricycle powered by pedal and electricity
Design and fabrication of Sub Marine
Generate Electricity from Dance Floor
Human Power Harvesting
Hydraulic Regenerative Braking System
Mini Bio Gas Fuel Turbine
Power generation using footsteps
mini homemade wood lathe machine
Perpetual Motion Machine 
Pedal powered refrigerator
Jaipur Foot
Automatic Car Parking 
Self Balancing Cycles and Unicycles
IE Engine
Electronic Fuel Injection
Study of cooling Tower
Air Compressed Cars 
Air Bike 
Mini Scooter 
Hydrogen Powered Vehicle
Escalator Compatible Wheel Chair
Fuel Energizer
Automobiles Engineering Projects
RC Helicopter
Carbon Solar Cells
Autonomous aerial vehicle
Build Electric Two Wheeler Bike
Biogas Powered Vehicle
Non Conventional Energy 
Manual Pump
Cogeneration 
Kinematic Project
Bicycle Sprayer 
Personal Flying Machines: This project is recently published in all the media publishing houses where they have shown image of person flying on lake with the help of flying machine.

Solar Object Lifting Jack : It is motorized electronic lifting jack which is powered by solar energy.

Air compressor at home:

Paddle powered mobile charger : It is based on dynamo chain concept.We have been using dynamo in bicycle from years. The best part about this is, mobile charger kits are available at online stores. You can learn the whole concept by purchasing a kit online and by disassembling it.