Indoor Home Surveillance Camera?

I live with a few different room mates. Over the past year or so, I've come home to find things in my bedroom a little out of place. I never made a big deal about it. It stopped for awhile, but today I came home again and found several things out of place - a clear sign that someone was in my bedroom while I wasn't here.

I want to find out who is trespassing into my bedroom and the best way I can think of is with a surveillance camera. I want to be able to record my bedroom during the 8 hours while I am at work so I can then watch the video when I get home.

Does anyone know of a good camera for such purposes? Preferably inexpensive.