I am pursuing my B.Tech and i am in my final year.
As a part of the final year project i am planning to build an UAV based on the QUADROTOR PLATFORM(design).This UAV will be able to detect the obstruction in its path and it will automatically maneuver itself so as to avoid the obstruction.I believe that making a fully autonomous UAV will be very costly so we  are planning to control the UAV using a remote control and the sensors incorporated in to the UAV will actually not permitt the UAV to move to a particular direction if there is any obstruction.
This is our basic FINAL YEAR PROJECT PLAN.

Can anyone suggest what components can be used.

i have got accelerometer(ADXL213AE) and gyroscope(ADXRS613).......
Pls help me....

If its not autonomous, why do you need accelerometer or gyroscope ?

As per what I understood from your post, all you need to do is to filter out servo signals that would result in a move towards an obstruction. Is stabilization also a part of your project ?

yes stabilization is an integral part of the project........

Since both are the same topic, please continue this discussion on the thread below.

http://www.rcindia.org/self-designed-diy-and-college-projects/quadrotor/

Wow there are so many quadcopter college projects on!!!
So basically you need batteries, motors, ESC's, and then Receiver transmitter..... Read about what I posted in another thread how to choose a battery...http://www.rcindia.org/self-designed-diy-and-college-projects/battery-specification-for-building-a-quadrotor-with-4-18aesc/new/#new