Dell outlet is great, but go to Dell's Off lease program.
I just bought a 3.4ghz p4, 512mb ram, cd-rw, optiplex gx270 for $319
www.dfsdirectsales.com
These are under 2 years old, corporate used, very clean. Comes with xp cd , mouse, keyboard, reformated, 30 day warranty and that's it. Nothing else, no manuals or anything. I checked mine out, reinstalled xp fresh. Works great. Thought that was a good deal.
A year ago, I lucked out on dell's outlet section and got a 3.6ghz, 2gb ram, 128mb video, dvd-rw, cd-rw, soundblaster sound card and a Dual 160GB Raid drive...... $500 (a year ago! believe that?)
I LOVE dells. I have boughten 4 of them all Refurbs or off lease. The oldest one is 7 years old and the only thing I replaced is the hard drive. I always turn them on, make sure everything is ok and then reformat and reinstall xp, gets rid of all that support crap and free offers and junk programs that you don't need.
You've got to watch these sites for a week or two at a time (several times daily). There's a lot of overpriced stuff on there, but when you see something good, you jump on it.