One of the things that I think all operating systems lack is a universal way for applications to display notifications. Yes, there are those pesky popup balloons on Windows, but using that to display notifications for things like new emails or messages is flat out wrong.
I’m not sure why all of the operating systems aren’t coming equipped with notification systems yet, but third-party developers are starting to take it upon themselves to create easy-to-use universal notification systems. Growl on Mac OS X started this whole idea, and it looks like something similar is making its way over to the Windows side. It’s called Snarl.
What’s nice about programs like this is that they provide a central location to enable and disable notifications for all applications that use the system. Right now Snarl ships with several different types of system notifications, and extensions can also be downloaded to add additional functionality. These extensions add compatibility for programs like Firefox, Pidgin, Songbird, Thunderbird, and more.
Unfortunately there aren’t a lot of supported programs at this point, but that’s because they partly rely on developers to take it upon themselves to add support for Snarl. There’s a developers section on the site dedicated just for that purpose, and hopefully in the future extensions for popular apps like Outlook will be available.