And to quote my other spiritual advisor, myself, free stuff is cool.
That being said, here's too much for free.
It's The New C Standard: An Economic and Cultural Commentary, which is a 1616-page monstrosity that meticulously details the C99 standard and (to use scientific terms) analyzes the ever-lovin' crap out of it. It charts and graphs and decision-analyzes and folds and spindles and mutilates every operator and bit of C esoterica, presumably with the aim of making better programs by showing where C's productivity trouble-spots are and how to work around them.
Unfortunately for the author, his publisher (Addison Wesley) found the book to be just too goldurned huge (books that thickness apparently can't run on standard book-printers) and dense for general consumption, so the author made the book available for free download.
The book itself is at http://homepage.ntlworld.com/dmjones/cbook1_0a.pdf. The download is only about 8 meg.
There's more about the book here if you wanna read more about its pedigree.
Long story short, if you plan to develop your own language and want an exhaustive and objective standard for the pluses and minuses of a very well-established language, or if you just want to be the biggest C smarty-pants in the room, start reading now.
Just remember to pace yourself by reading one page every morning when you start work. That way you'll be the official C Big Kahuna(tm) at your company around mid-November 2009.