Linux.com's Nathan Willis wrote a short review of the top photo managers. Whilst I wish that there is a Linux port of Apple's iPhoto, Google's Picasa, albeit non-open source, seems to be the best of the bunch of free photo management applications on Linux.
Personally, I just upload my photos to Flickr and use its on-line photo management tools. Don't get me wrong, I use photo management tools but only for my must-keep photos. The others, mostly for blogs, are stored via Webshots.