rotateMe is a cool app that rotates the screen when the orientation of the phone changes. The problem, as it is with some many other cool freeware apps, is that it's unsigned.
I found some great directions on setting up Mobile Signer which allows you to sign apps directly on the phone. Rather than using the included cert files though, I created my own at the Symbian Signed website. It's pretty easy with the directions listed under the "problems" section of the tutorial.