I'd say go with a 1.3-2 megapixel camera. That should be plenty for posting online. A 3 pixel would make nice 8*10 with a decent printer and 8*10 is usually huge and unnecesary...
I have this camera (Canon) in the A20(2.1 megapixel) spec this is the A10 (1.3) :
http://www.buydig.com/shop.php...abber
Might be too much but I really like mine.
Edit: I read over the posts again...and then looked online...Canon makes a great product and it looks really good, the camera and the pics that is. Canon is more expensice though. I bought mine 2 years ago when I went to Boston after looking through a consumer reports, I think it cost 300 dollars for batteries, Photo Editor, Some paper, and nice San Disk (use google).
I shied away from HP Kodak when I read a consumer reports before going to get a camera because they said there were better cameras to get, I have no idea what they are like now, but since you are looking used.... HP does have some deals though 150$ for a 2.1 is nice.