Growl is a popular, and free notification package for the Mac that is supported by a wide range of programs (e.g. Adium, Chax, Cyberduck, Dropbox, and many more). Its messages appear as transient floating bubbles, typically in the corner of the screen, fading away after just enough time. The current version (1.1.6) reportedly works relatively well in Snow Leopard. However, it runs in the less efficient 32-bit mode and some features don’t work properly. Luckily, the Growl team is hard at work on a new update (version 1.2) which is being targeted for release tomorrow.

If you don’t already have Growl running on your Mac, you really should.

Update: The Growl 1.2 beta is now available.