Meet the Buffer Cache
I realize that most hard-core backenders will already know most of this but, with all of the posts that have entered my aggregator relating to sprocs and ad-hoc sql, I thought that I'd take this opportunity to add a link to an article I wrote a few years ago which discusses what gets cached (and when):
http://www.msdnaa.net/Resources/Display.aspx?ResID=825
(Listening To: Out of the City (Hardkandy Mix) [2 Heads / Chillout Sessions Vol 4 (Disc 2)])