Picasa Image Viewer
Picasa is a free image viewer and organizer distributed for free by Google. Google didn't actually invent the software, but bought it and improved it.
When you first launch the Picasa image viewer the software scans your system to find all graphics on your system. This includes both photos you might have in your MyPictures folder or elsewhere on the hard drive and also any other type of graphics. It then sorts them into an easy to view system.
Picasa also makes it easy to share images and publish them to select photo web sites. It would be nice is Picasa let you upload photos into picture galleries on your web site in addition to just the photo services it usees.
One handy sorting feature is the star rating. In Google's words, "Give a gold star to any photo you love: it turns your favorites into visual standouts at a glance. Picasa even has a star search that reduces your entire photo collection to the best of the best in less than a second."
Picasa also lets you sort one image into more than one album. This is kind of like how you can apply labels to email in Gmail. The picture can be accessed through multiple albums but it isn't copied on your hard drive to take up more space.
Click here to learn more about Picasa.