Designer/Developer Christopher Lobay has been hard at work making some excellent Styles for the system notification app, Growl. Growl displays temporary, floating notification windows above your desktop to let you know about things like new messages, completed downloads, changes in Skype availability, etc. Many applications have Growl support built in, so if you're not using it already, you should check it out. Once you do, you'll want to customize the way it looks, and that's where Christopher, among legions of others, comes in.
Published a while back, the first Growl style I want to highlight is "Basics." Basics provides a very minimalist black background on which it animates the icon of the application responsible for the notification. If you, like me, have grown all too accustomed to notifications popping up around your desktop, this little bit of animation (just a slide across the bar) can make the popups much more eye-catching, without being distracting. It is, as its name implies, basic, but has an air of class not always seen in Growl styles.
Second -- and brand new right now -- is "Mono." This latest one is even more subdued, with a very nice bezel and it's the text that animates rather than the icon. This has much the same eye-attracting effect but is even less distracting. It's some great work by Christopher, and definitely worth a peek if you're using Growl. Both styles are available for free, so go get 'em!