XnView MP - XnView is a free software that allows you to view, resize and edit your images. It supports more than 500 different formats!
SageThumbs - SageThumbs is a powerful shell extension allowing to preview enormous amount of image formats...
JPEGView - JPEGView is a small and fast viewer/editor for JPEG, BMP, PNG, GIF and TIFF images.
ThumbView - ThumbView enables image thumbnails and tooltips in Microsoft Windows XP Explorer (does not work on...
IrfanView - IrfanView ... one of the most popular viewers worldwide.
Icaros - Icaros is a collection of lightweight, high quality, Windows Shell Extensions