On my side (WinXP), data directory is on D: drive, folder BitcoinData, so "Target" field for shortcut is:
"C:\Program Files\Bitcoin\bitcoin-qt.exe" -datadir=D:\BitcoinData
Does anyone have any idea how to change the default data directory on a Mac? I'm not aware of a "Target" parameter when launching apps in OS X. I've tried googling it but come up with nothing.