Battery Saver is a homebrew app that automatically turns on Airplane Mode on a schedule you specify.
So, for example, you can train your Pre to make Airplane Mode kick in at 930 every evening and then go off again at 730 the next morning. All night long, your phone isn't chewing up the battery with Wi-Fi, Bluetooth, and cellular signals -- great, if your phone is sitting in your briefcase instead of on the Touchstone.
Of course, that means your phone won't alert you to any incoming calls or texts in the middle of the night, but in all likelihood, that's an additional advantage.
I've been using this app for a couple of weeks, and it has dramatically extended my battery life, since I'm notoriously bad at remembering to charge my phone. If only the iPhone and other phones had something like this.
Oh, and since this is a homebrew app, you'll need to follow my handy guide to installing homebrew apps on your Pre.