hello. Im a fifth year computer engineering student now. and We are now beginning to plan our thesis.. and im planning to use at mega 168 microcontroller. can you help me to decide what project is the best to make. a not expesive project.
How about a combination alarm clock/window shade operating device.
Wakes you up, opens the shade in the morning, closes them at night.
Add a barometer to tell when low pressure is arriving so you warning time to close windows before the monsoon arrives also.
that's cool.. thanks for the idea sir.. how about sir a thesis project that is useful in the school.. could you give a project idea?
thanks for the reply.. 
You might do some sort of robotics project. There is tons of info on how to do them and they don't cost as much as designing a mass spec. Another approach is to use the arduino to monitor some physical parameter ( temp, press, light...) and cause some physical process to start or stop or change according to what the input is. You can also log the data coming through and graph it and go crazy mathematically analyzing it!
Better still all of the above! Lots of people here do a hell of a lot of pretty sophisticated stuff on the cheap, and don't have anything close to an EE degree.
Well why don't you ask any of the other departments if there's anything they need?
Maybe the drama guys need some kind of lighting control for the theatre, or the sports guys might appreciate goal-line or tram-line in/out monitoring, or the geography guys might appreciate some weather monitoring / logging. Your mechanical engineering counterparts might be looking at CNC control for some machinery?
Take a walk round the campus- but look at it with new eyes and ask yourself how anything you see could benefit from your skills. I'll bet you come up with dozens of ideas!
Edit... Have a look at the Week 2 Sensor Walk blog and Fantasy Device assignment on this course at NYU... it might spark some thoughts for you.
Good luck!
Jim