Although it is really old now, the C language is still extensively used for scientific computing (and in my opinion is much better than fortran). I enjoy coding C and reading about it. These few links are very interesting if you want to improve your skills. I will continuously update this page so add it in your bookmarks and come back from time to time ;-)

• Bien programmer en C : strict/efficient methods for programming in C. Really worth reading, if you read french…
• The C programming language : C bible, you want this book if you write C
• Cours C de l’IDRIS : Nice C tuto, in french.