Google's Picasa is all about photos -- it helps you instantly find, edit, and share all the pictures on your computer. Although it isn't released as open source it is free to download and use from Google's Web site. The new version 3, which is currently in beta, is available for Windows as well as Linux.
Version 3 has some great new features, including a new retouch tool to remove unsightly blemishes from your photos. If you don't want to download the beta, the previous stable version is still available.
This video gives you an idea of what Picasa can do, how it works, and how it looks. Once you have watched the video, why not go and download Picasa and give it a try yourself?
Ogg Theora (right-click to download)