Craig [1] (via Brad) found Alvio, a really cool place to order computers online. My favorite is the page that lets me configure a barebones P4 system from scratch [2] and then they assembly it, test it and guarantee it for a year.
The thing that I like most about Dell is how easy it is to configure computers online. To be able to configure one from the ground up w/o any OSes et al is *way* cool.
[1] http://staff.develop.com/candera/weblog2/permalink.aspx/9090a88d-dd58-4310-bb33-85cdc0b121b6
[2] http://www.alvio.com/smoreinfo.asp?iid=941