If you’ve not used Flickr yet, do. It’s brilliant.
When I first signed up I didn’t really like the emphasis on the social aspect of it, I would have preferred to be slightly more like del.icio.us, where the social aspect is emergent rather than integral, just putting my photos up for my own reference and ease of insertion into my blog; but as soon as you start getting comments from people on your photos and start joining groups Flickr really takes on a life of its own.
Overall an excellent, excellent piece of software that goes as far as you need it to and beyond (not to mention the open APIs which some enterprising chap has used to make a Flickr screensaver). Great stuff.
I agree: Flickr is brilliant.