I am a big fan of the gimp. It's open sourced, free, powerful and difficult to learn. It's also really big and takes a long time to load. Since I spend most of my time editing pictures of the kids, removing red-eye and cropping, I don't always need the power of the gimp. So I was excited to find FastStone's ImageViewer.
"FastStone Image Viewer is a fast, stable, user-friendly image browser, converter and editor. It has a nice array of features that include image viewing, management, comparison, red-eye removal, emailing, resizing, cropping and color adjustments. Its innovative but intuitive full-screen mode provides quick access to EXIF information, thumbnail browser and major functionalities via hidden toolbars that pop up when your mouse touch the four edges of the screen. Other features include a high quality magnifier and a musical slideshow with 150+ transitional effects, as well as lossless JPEG transitions, drop shadow effects, image annotation, scanner support, histogram and much more. It supports all major graphic formats (BMP, JPEG, JPEG 2000, animated GIF, PNG, PCX, TIFF, WMF, ICO and TGA) and popular digital camera RAW formats (CRW, CR2, NEF, PEF, RAF, MRW, ORF, SRF and DNG)."
It's practically microscopic(3MB) compared to the gimp(40MB) and its fast. The full screen mode is really cool and intuitive, once you get the hang of it. There are a ton of shortcut keys that make browsing a little easier. Red eye removal and rotation are a snap. The cropping feature is cool because it allows for you to set the crop size to monitor resolutions. Great for getting a picture of my daughter in her bumble-bee costume for my wallpaper. It comes with dual monitor support, so you can do full screen on one monitor and look at the image viewer on the other. It will even let me link to an external program, if I want to edit the image in something more powerful.
And don't forget, this is a portable app. There are no ties to the registry. So next time you take your USB drive over to your parent's house to show them the pictures you just took of the grandkids, you'll have a great image viewer to view them in.