I'm on vacation right now, so I can't actually test this, but I'm going to get Skype, and I wonder if I can use my xbox live vision camera as a web cam? Or do I have to buy an actual webcam?

You can use it as a webcam but you need a separate mic since the Vision Cam doesn't have one built in.

Yep, you can. Windows should detect it automatically and install the drivers for you. (I use mine as a PC webcam all the time)