All writing benefits from warm-ups. I free-write on every project because it saves time in the long run -- see my post on LSD. The Egg Timer widget lets me time my free writes simply and easily. It's very cute, and stays out of your way on the Dashboard.
You can also use Egg Timer to conquer procrastination, as "Kick procrastination's ass: Run a dash" suggests.
If you're a Windows person I know there's a freeware app called FM Egg Timer. I haven't used it, but it should do much the same thing.