Just bought my new components from a combination of TigerDirect and NewEgg. About $350 altogether, before rebates. Went with AMD instead of Intel because 200 mhz faster core was $40 cheaper that way.
Specs:

AMD Athlon 64 X2 5400+ Processor - 2.80GHz (dual core)
2 GB DDR2 800 Mhz (2x1 GB dual channel)
GIGABYTE AM2 NVIDIA nForce 570 SLI MCP ATX AMD Motherboard (open box for about $100 off)
XFX GeForce 8800GT XXX 256MB 256-bit GDDR3 PCI Express 2.0 x16 HDCP Ready SLI Supported Video Card (just one for now but the potential is there to add another down the road when it's cheaper).

I saved a little money by deciding to use my current case rather than buy a new case as part of a barebones kit.

Compare to my current rig:
Athlon XP 2800+ 2.1 Ghz
1.5 GB DDR PC3200 RAM
GeForce 6600 GT AGP

Someone's getting ready to kick some AoC arse!!