I've actually been looking for the same thing; unfortunately I didn't find any useful "Anatomy of a Miner" document (I might write one myself once I get my head around it fully), but taking a look at the code for pyminer is probably a good bet - it seems to be the simplest and most readable one out there. Satoshi's original paper is also definitely worth the time, if you haven't taken a look at it already, to get the broad picture of what all this hashing actually achieves.