You should make some boverflow challenges that they download and have to get the password to enter into the web
Well they would have to be hosted on a shell account and I would have to set up a chroot jail and get everything set up. As the program would be open source, so is there much of a point to letting them have the source? They'll just be able to get the password. I could make some programs they need to disassemble to get the password though.