i was looking for a good book to bring me up-to-date on recent changes to c and the best suggestion i received was to get the latest edition of harbison and steel's book (which includes c99).
i don't know if you know the book - an older copy is on my desk and it use it regularly when working in c - but it's part introduction and part informed guide to the libraries. it's not a "friendly" book (it's not for "dummies"), but it's well written and surprisingly compact for all it contains (at least, the copy i have is; i am waiting for delivery of the latest version).
Last time I wrote anything in C was on Netware NLMs, and it has been long enough that I have mostly forgotten what I knew.