Apple has released the Digital Camera RAW Compatibility Update version 2.7 for OS X v. 10.5 Leopard and OS X v. 10.6 Snow Leopard. The new update adds RAW support in OS X, Aperture 2 and iPhoto for the following cameras:
Canon EOS-1D Mark IV
Canon EOS 7D
Canon PowerShot G11
Nikon D3S
Nikon D300S
Nikon D3000
Additional details can be found on Apples support pages for OS X v. 10.5 Leopard users and OS X v. 10.6 Snow Leopard users.