The Growl Project’s Growl ($2) has long been worth installing early on almost any new power user’s Mac. Now, the notification tool has been updated to version 1.3, and there are some significant differences. First, it’s only available from the Mac App Store. And instead of being free, it now costs a couple of bucks. But there have been updates to the features, too, so you’ll probably want to shell out the couple of bucks for it.
Growl’s premise is pretty simple: it alerts you when supported apps take certain actions, such as when you receive an IM when you’re using Adium. Now, instead of just a preference pane, Growl is a full app. Notifications queue up in the Rollup, allowing you to see what happened when you were away from your computer. There are a bunch of different presentation styles, and notifications can even be sent from Cocoa, AppleScript, or over the network. If you’re using Prowl on your iOS devices, the alerts will show up there as well.