I would agree that logitech are the best rand to got for, if you can afford 40-50quid for a webcam go for the quickcam pro 9000 it's fantastic, to be honest at the full 2megapixel it is a bit much for most web chat but even at lower resolutions it is crystal clear even in low light and has a built in mic that works reaally well.
On top of that there are loads of silly effects you can appply to the video and the avaters are great fun, just go to
Http://www.youtube.com and do a search on ligitech quickcam pro 9000 to see some if them.
Though having said all that if all you want is a camera for occasional video chat then proably is a bit much and one of the cheaper logitechs would do