A nice little tool that does exaclty what the tile says. You can view thumbnails for dds files direcly in Explorer, which makes it very convenient when working with textures. For skins, tracks or cars.
You can find the nvidia tool there: http://www.nvidia.com/object/dds_thumbnail_viewer.html
And if you want (much) more features, you can go for this one: http://mysticcoder.net/mysticthumbs.html#download
EDIT: eventhough the mysticthumbs does support a lot of formats, I find it a bit too agresive/intrussive. For my taste..
You can find the nvidia tool there: http://www.nvidia.com/object/dds_thumbnail_viewer.html
And if you want (much) more features, you can go for this one: http://mysticcoder.net/mysticthumbs.html#download
EDIT: eventhough the mysticthumbs does support a lot of formats, I find it a bit too agresive/intrussive. For my taste..