I recently tapped (and quickly consumed) my own pumpkin beer recipe. It was the result of reading about a lot of other pumpkin beer recipes out there and developing my own. Last year was my first run, and I greatly improved upon it this year. It uses a lot of the same ingredients as pumpkin pie including pumpkin, cinnamon, nutmeg and allspice. I really liked the result, and apparently everyone else did too. I had a small gathering of about 18 people and that was enough to kick the whole 5 gallon keg.
What I ended up with was a rich, sweet ale, and the pumpkin really came through. Read all about it and get the recipe on my site: http://www.inorganik.net/?p=484