After installing Snow Leopard and a few extra applications that I use daily, here is the breakdown of 64-bit vs. 32-bit applications.
Sadly, none of the third party applications are 64-bit yet. Luckily, Xcode 3.2 (included on the Snow Leopard install DVD) now defaults to generating universal binaries with the x86_64, i386 and ppc architectures enabled for Release builds, so we should be seeing a lot of third party 64-bit apps soon.
iMac:Applications kennu$ file QuickTime\ Player.app/Contents/MacOS/QuickTime\ Player
QuickTime Player.app/Contents/MacOS/QuickTime Player: Mach-O universal binary with 2 architectures
QuickTime Player.app/Contents/MacOS/QuickTime Player (for architecture x86_64): Mach-O 64-bit executable x86_64
QuickTime Player.app/Contents/MacOS/QuickTime Player (for architecture i386): Mach-O executable i386