I'll add 409 and Fantastik (household cleaners) to the list. I've never tried 409; but it's supposed to work about the same as Fantastik. My experience with Fantastik is that it takes about 24 hours if you want every little bit of paint removed... Definitely not as fast as the other methods suggested, but much safer.
I've heard of others using Westleys, oven cleaner, and Castrol Super Clean...
This is the most extreme solution I've seen (NOTE THAT I DO NOT RECOMMEND THIS):
http://www.scaleautomag.com/sca/community/forum/topic.asp?TOPIC_ID=6566
Like pretty much everything in the hobby, it's all a matter of personal taste... as long as it works, it works.