I am currently running Mint 9, but I think the advise to go for 'UVC' webcams would almost guarantee functionality with Linux, and with Skype under Linux. So, for instance, I successfully used the recent crop of Microsoft 'Lifecam' webcams with Skype on my Mint system (Lifecam Cinema and Lifecam HD-5000). They are top-of-the-line webcams that happened to be on sale in Canada over the last few months. I am very pleased that I don't have to sacrifice the 'best' video quality on a consumer webcam for the sake of Linux compatibility!
On the other hand, it *has* been a bit tricky for me, in Mint 9, to get 'pulseaudio' working properly and consistently -- I ended up creating a little auto-start script that do this. This was not Skype's fault or the webcam's fault, but it needed so that the microphone works for Skype. The other small annoyance is that my system occasionally 'forgets' which device is supposed to provide the primary 'microphone input' -- and I have had to adjust it to point back to the webcam mic.
There is nothing more dangerous than a bored cat.