Google sucks at knowing that I want C and not CPP. Anyway, it's been a while since I've programed in C. Does anyone have a good small refresher in programming C? Preferrably online, not a paper book.
The best refresher on C is to go code something. I looked in my C folder (I have a programming folder, with a folder for each language I play with) and I have nothing of value there, so I did a quick Googling. this (http://en.wikibooks.org/wiki/C_Programming/Beginning_exercises) looks like a good crash course, and here's (http://publications.gbdirect.co.uk/c_book/) a book, although I haven't really looked at it.
The K&R (1) book is the classic textbook, and it's also good as reference material. There's also the man pages. It's useful to poke around /usr/include and /usr/lib if you're on Unix, and it's also useful to refresh yourself on libc (2).
There's a ##C channel on freenode which is good for language-specific questions. Don't be scared off by the newbies - the people who answer questions usually know C pretty well.
I also wrote a packet sniffer and an IRC client in C. I uploaded them to sidoh's server. (3)
(1) http://en.wikipedia.org/wiki/The_C_Programming_Language_%28book%29
(2) http://en.wikipedia.org/wiki/C_standard_library
(3) http://ktm.sidoh.org/code/
Nota Bene: In addition, I'd strongly recommend familiarizing yourself with gdb and assembly. Also: linking, loading, and dynamic libraries. And, of course, memory management, if you're not familiar with it already.
The IRC C and UNIX crowds are almost certainly the wrong people to ask. These people won't help you with a refresher, they just want to be around each other, share links, and idle. Anyone who asks newbie-like questions will be severely punished.
The best place to look for help are programmer forums. This forum and rohitab are great programming forums.
How did I forget stackoverflow (http://stackoverflow.com/)?
I think the best way is to jump in headfirst. Think of some project that sounds fun to you and go for it.
A sudoku solver is a pretty nice choice because it's somewhat simple, but still requires good use of some data structures and algorithms.