Apple just released an update for RAW camera support for Mac OS X Leopard, Aperture 2, and iPhoto '08. With this new update, the following list of RAW-format cameras are supported:
Canon EOS 50D
Nikon Coolpix P6000
Apple also notes that this update "addresses issues related to specific cameras and overall stability." You can download this update by opening up Software Update (Apple menu > Software Update) or by downloading the installer package from the Apple Support downloads site.