A post at Mac OS X Hints
lists some bizarre shortcuts that appear to be new in iTunes 7. The shortcuts apply to selecting the various content sections such as Music, Movies and the Store, but what's strange is that if you have any playlists which begin with the same letter as the shortcut, the playlist takes precedence. For example: the letter M (amongst others) can take you to your Movies section, but if you have a playlist titled "Mashups," the letter M will take you to the playlist, not the major content section.
These shortcuts are very strange indeed, and it would be nice to have a more unified and universal list tucked away under a menu somewhere, so the shortcuts worked no matter what you were doing in iTunes, or what was selected. Still, if you're interested, check out Mac OS X Hint's list
of shortcuts found so far.