Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
If you really want an iSight, try ebay or craigslist. Would probably cost you 150-200, so doesn't seem worth it to be for a mini. Check out logitech, there are probably some $30-60 ones which would be fine.
 
I have heard the Xbox Live Vision camera is actually a really good web cam. It supposedly works with macs, although Microsoft doesn't tell you that. You get a decent quality webcam for $40 (IIRC), not a bad deal
 
I've got one I never use. I should probably put it on Craigslist. Unless you're interested?
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.