Growl
Growl, the excellent system-wide notification system for OS X, is now available exclusively via the Mac App Store.
I use Growl a lot, mostly via growlnotify, and the new version is an absolute bargain at £1.49/$1.99.
I’m wary of the upgrade, though. A notification system should be completely invisible until it has something to tell you, but—unlike earlier versions which were configured via a System Preferences pane—Growl 1.3 is a full-blown menu bar app.
