RawkSD allows you to install custom songs as DLC onto an SD card, to be played in Rock Band 2. It also allows importing songs from Rock Band 1 and all Guitar Hero games.
Changelog
v2.00
Guitar Hero 5, World Tour, Metallica, and Smash Hits support added
RawkSD Patcher has been updated to support ripping from Playstation 2 discs
Complete fixes made for custom charts on all difficulties
It's suggested that you use the Replace Files feature to re-import all your custom audio and charts
More tagging info done (thanks again to tw3nz0r and BHK)
The Wii RawkSD Installer has been totally revamped
No more need for the PC during installs.
Added integrated disc ripping support to SD and USB
New option to backup and restore your savegame