Growl is a really cool app for OS X. Described as "a global notification system for Mac OS X. Any application can send a notification to Growl, which will display an attractive message on your screen. Growl currently works with a growing number of applications." I'm using for ecto blog post messages, Apple Mail app, and iTunes (display's next song and album art). It is saving me time switching back to apps for status type info. It also provides a consistent UI for apps to interact with the user.
