From Finer Things in Mac I found out about these two new features in Snow Leopard.
That is incredibly useful for those of us who write emails in different languages. I usually write emails both in Swedish and English and earlier I had to open the Spelling and Grammar window and change the language accordingly. No more! Now Snow Leopard will do that automatically for me. Hurray!
At home I hook up my MacBook Pro to the pair of crystal-clear, eyeball-shaped speakers created by Harman Kardon and Apple that I got with my G4 Cube, and being able to choose the output by just opt-clicking the volume icon in the menu bar makes that easier.