FastStone Image Viewer
Note: This review addresses v4.0 of the software.
If you only use the photo tools built into Windows, browsing through your photos quickly becomes tedious. FastStone Image Viewer displays pictures lightning-fast and lets you browse through them all in Windows Explorer-style fashion. Run the program, go to the folders where you want to browse, and all your photos are displayed immediately, with very little delay. You'll see thumbnails of them all, and a preview screen. To see any full screen, double-click it.
If all FastStone Image Viewer did was display images, it would be well worth the download. But it does much more than that. You can crop, rotate, and resize pictures, as well as send them via e-mail. You can also create slide shows. And the program will also let you convert between file formats.
One of FastStone Image Viewer's greatest strengths is the wide variety of file formats it supports. It can handle just about any graphic or photo file format you've heard of. In addition, it previews videos as well, so you can use it as a full multimedia viewer, not just for photos.