I just learned of some cool software called Watchflag from Jason Langridge's blog. The Watchflag software lets you create custom alerts for incoming messages as they arrive on your Windows Mobile phone. Although you can receive alerts on email in subfolders, as he points out, you can also do so much more, too.
Using rule-based notifications, you can have different mp3 sounds play based on sender or subject, have the display light up, have the phone vibrate, or have alerts repeat, and much more.
This could be really handy to help you sort through your influx of email, making sure that you don't miss that all important email from your boss or the meeting request from your department head. But personally, I like some of the examples uses that Watchflag comes up with, like a loud siren when you server goes down or a fight song for score updates from your favorite team.
The software is available for a free trial which you can download straight to your phone from m.watchflag.com.