Ask HN: Learn C by Small Exercises?

I'm looking for a set of small exercises to re-learn C. I'm not interested in tutorial-style "please make a for loop" because I already committed (as in crime) many lines of C, but it's been quite a time ago. I'm aiming at exercises small and completable, like small projects. Any book suggestion would be nice too (before I was doing the C, I had read 21st century C - this is the level I'm on c.a.), or maybe an exercise suggestion?