For the last, hmm, 6 months I\'ve been reading into Programming in C, I got myself K&Rv2, BEEJ\'s socket guide, Expert C programming, Linux Systems Programming, the ISO/IEC
Code Golf and Project Euler are good - but they are more about problem solving and maths than programming.
Find an Opensource project (probably not the Linux kernel) that you are interested in, download the source and try and use it. Ideally something that is a library rather than an application so you have to learn how to read it to use it with your own stuff.
Don't worry - It only takes about 10 years to become a good programmer.