Snarl is a small application which allows other applications to send unobtrusive and pretty notifications to the user in an easy and unified way. It's not a standalone system like its cousin dotWidget, which I also wrote about recently, but it does allow the unconventional user, who likes to dig in and get their hands dirty, a way to make all sorts of eye-pleasing notifications from applications which have some sort of plugin interface.

Snarl comes with two example notification plugins; Snarl Clock (a clock) and SnarlTunes (an iTunes interface). There is a somewhat active forum around Snarl where you can find third party notification plugins which may fit the bill for your intended use. Snarl isn't well supported yet, but is a really slick idea which could use the attention of more developers.