Logitech make good, reliable, inexpensive webcams - I've got a QuickCam Chat - which has an adaptable bracket to sit nicely on a flat surface, or hook over the top of a TFT moniotr (not many do bith).
Picture quality is fine - but for decent sound quality use a headset.
I've also got a Logitech USB Headset20 headset - plugs neatly into a fron USB port - automatically switches to itself when plugged in - and back to speakers when removed (all by software, not a mechanical switch.) There's a slightly more expensive model which has a volume control in the lead too. Sound quality is good enough to listen to music too.
A headset is essential for good two-way audio - it prevents delayed feedback which is both annoying and off-putting.
Very happy with the combination.