I've been using it for my picture galleries and with a 1 gigabyte size limit initially and unlimited albums, it completely blows away flickrs paltry initial offerings. Plus, flickr, photobucket and others are blocked by many corporations ( including the one I work for ) so you can have more chances for people to see your pictures from their work pcs :)
If you already have a gmail account, signup is simple.
http://picasaweb.google.com