UnitTest++ is worth a look. It lacks features compared to some of the other frameworks mentioned here, but the simplicity is nice -- especially if you're just getting started.
I believe it was developed by Noel Llopis after writing the article mentioned in http://gamesfromwithin.com/?p=29. It is pretty easy to port to a multitude of different compilers/platforms -- useful if need to target something other than a PC, be it a game console, embedded device, or otherwise.
The mailinglist has been quiet for a while now, but every so often there are questions, patches, and/or a new release, and people who ask questions are usually answered quickly.