Skype is another very popular option -- Skype is available both for Windows and MacOS, and it does video conferencing. Some people have reported that it has problems less often than AIM/iChat.
In terms of cameras, Logitech is certainly a great recommendation as made above. Another very inexpensive option that is compatible with pretty much everything is the XBox live camera. I think it's available in a kit with a headset for about $30-40 (or you can use the internal mic if you have a notebook -- most of them have microphones on the bezel surrounding the screen). It works
with OS X and Windows and shouldn't need custom drivers on either.
EDIT: Reading your post above... starting with... 10.4.9, I think, a number of USB cams are supported in OS X without drivers. Pretty much any camera that runs in OS X without a driver should work in iChat. This
this may be necessary for cameras that require their own driver. I'm pretty sure that the Xbox cam and most of the logitech ones work out of the box, though. Dynex I know nothing about. I've never heard of the brand before.