Windows only: Photo geeks out there know how valuable raw image formats can be, but the Windows Imaging Component doesn't have native support. The free FastPictureViewer WIC codec pack adds RAW support to XP, Vista and 7.
By default, Windows Explorer won't even show thumbnails for images in raw format, nor does it support slideshows or previews in programs like Windows Live Photo Gallery or Windows Media centre. FastPictureViewer WIC Codec Pack is a one-time install that supports 20 raw image formats from more than 13 camera manufacturers—so no matter what camera you may have now or in the future, your system will likely support it. In addition, it provides all of these codecs for 64-bit editions of Windows, which camera manufacturers don't always do. So even if your camera doesn't provide the support, you can probably find it here.
FastPictureViewer WIC RAW Codec Pack is a free download, Windows only.