Gallery is an online photo album. You can install it yourself on your webserver, and it will allow you to upload pictures and have others make comments on them. And while I wouldn't swear to it, it looks to my untrained eye that even such lumniaries in the "post family pictures online" game as Ofoto are based on Gallery.
It is written in PHP and is extremely customizable. The website for Gallery is http://gallery.menalto.com