one thing you might look at is you most find "barebones" deals that are a mobo/cpu/RAM combo. see here:
http://www.pricewatch.com/m-349.htm
I'm assuming you are building because you have some parts to reuse from and old box? If not, if it's just because you wan to pick every component, look at some of the white box builders sites and they will assemble and burn in for you... this is a pretty good deal.
If you are resuing a case and power supply, make sure it will drive the new stuff... you may need a new one.