XnView is freeware software that allows you to view and convert graphic files. It's very fast and easy to use. But more importantly it supports more than 400 graphics formats!

Changelog:
Added:
* Thumbnails use transparency/alpha of picture
* Add Panasonic RAW format
* XMP in clean dialog
* Hidden setting, CopyClipboard=2 (filename+image), =0 (image), =1 (filename)

Changed:
* 'Search IPTC' use now all IPTC fields
* All web templates are now in utf8

Fixed:
* Some problem with file list refresh
* histogram
* Camera RAW
* Slideshow with audio
* 'Add text' with 32bits picture
* some minor bugs

Download: http://perso.orange.fr/pierre.g/xnview/endownload.html

Nice alternative to ACDSee or similar paid solutions.