Battery notification messages in Windows 7
Something I didn't know but find very, very cool: Windows 7 lets you know when you should consider replacing your laptop battery.
My laptop is about a year old and I haven't seen the message yet, and I hope I won't see it for a while, but of course when my battery goes bad I'd rather know than perhaps blame some new program or device for the shortened battery life.
If you're still discovering all the things you can do with Windows 7 like myself, and would like to see what you can tap into as a developer, head over to the Windows Developer Center on MSDN and browse around - there is a lot of fun stuff there.
Enjoy!