There's only a couple (last I knew) Logitech webcams that'll let you broadcast higher definition video over Skype. Maybe check Skype's website to see what models are compatible. I don't recall at the moment what resolution that would be.
I got a Logitech QuickCam 5000 something or other a couple years back and it works great in all kinds of lighting (even none) and is Skype certified. Muffles background noises. But it's not on the list of cameras that Skype will send higher definition video from. Curses.