I always like Larry Ullman's books, especially his PHP and MySQL one. When I was learning C, his book was really helpful: http://www.larryullman.com/books/c-programming-visual-quicks...

C as a language is pretty simple to learn. Using C in practice is where things can be tricky when you need to dance with the compiler and work on low level systems where a datasheet is always open, and if you haven't had your "Pointer Enlightenment" you're toast. Domain-specific books are key there and just continual practice.