Free Acid Loops: 20 free loops every month for registered users.
Smart Loops: "Access to free Drum Sample Sets in SoundFont, SFZ, and DR-008 formats." with registration.
Break Beats Drums: Almsot 120 loop packages, and lots of other categories as well.
Directionsinmusic: Get your GarageBand (Apple Loops). Free drum and perc loops here! Played by Michael Blair (ex-Lou Reed, Tom Waits, Elvis Costello, Ryan Adams, etc) and recorded, mixed and produced by Chris Bell.
Macloops: Jungle, Latin, Rock, Reggae, Chillout, Hip Hop, and Heavy Metal GarageBand Loops