I really enjoy CppUTest. It was written by James Grenning who is one brilliant engineer if you ask me. He also wrote the fantastic book "Test Driven Development for Embedded C" which I would highly recommend to anyone, even non-embedded developers.

I used CppUTest on a c++ project to test algorithms for image and video manipulation. It worked fantastically, very easy to learn, and it helped test drive and optimize the algorithms. Highly recommended.

Edit: fixed typos, typing on phones is hard.