Flickr. Or for a second choice, Flickr. 3rd alternative? Flickr. There really is no other choice. Fast, simple, easy to use, edit facilities, excellent tagging, brilliant forums for groups, and then there are the BigLab options to play around with your images. You can also embed into a variety of blog options, RSS feeds... The main limitation for the free account is the 200 limit and also the lack of lots of folders, but you could always create a second account if necessary.