As far as a main project, I would choose something new and independent. Think of that crazy idea you've been playing around with for a while, but haven't had time to implement.
Another thing that often gets overlooked is a side project. My internship work level tended to be very cyclic. Whenever my main project was stalled for one reason or another, I had little to do(I ended up roaming through the code base). Find an incremental project for this. Bugs and small features may suffice.
Finally, recruiting. Posting on sites like this is a good start. The type of students you want will find it. Also contact the career centers or CS departments of the specific schools you like. Most have some sort of system in place. Recruiting begins in September in a lot of places.
Send me an email if you want to pick my brain.