And it doesn't run inside of the OS... which is nice I guess if you can't boot into your OS. Very simple interface too. You can follow this link to download and install it:
How-To Root your stock 2.1 Droid
Thats where I learned how to root my phone too. Nice complete writeup. It mostly directs you on how to root your phone but the first half of the first post in that thread talks about simply flashing SPRecovery.
* I should mention that the linked writeup shown above is a Motorola Droid Stock 2.1 writeup.