Jgarzik's CPU Miner
Supports Windows and Linuxbitcointalk.org thread
A new CPU miner is now available, making use of the new 'getwork' RPC command.Donations: 1BrufViLKnSWtuWGkryPsKsxonV2NQ7Tcj
In the beginning, this is intended largely to demonstrate a 'getwork' miner. It is written in straight C, with minimal dependencies (libcurl, jansson).
It has successfully generated blocks on testnet, mainnet and almost all pools.
UPDATE: This has largely been superceded by Con Kolivas's cgminer fork. See cgminer's official forum thread for updates and details.