I figured I'd share the wealth, along with pickup any good places from everyone else for both PC Upgrades, or mods. So, I'll start it off:
(IN ORDER FROM BEST TO WORST, IMO)
Upgrades / Sales
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[url:4c609]http://pages.ebay.com/catindex/computers.html?ssPageName=MOPS5:CN22003[/url:4c609]
http://www.pricewatch.com
[url:4c609]http://www.amazon.com/exec/obidos/tg/browse/-/541966/ref=gw_br_pc/002-0541365-1207252[/url:4c609]
http://www.newegg.com
http://www.tigerdirect.com
http://www.cyberguys.com
Modding
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[url:4c609]http://www.twistedmods.com/modules.php?name=Sections&op=listarticles&secid=1[/url:4c609] (GREAT how-to guides on PC mods)
http://www.xoxide.com
http://www.frozencpu.com/cgi-bin/frozencpu/index.html
http://www.computuning.com/
http://www.coolerguys.com/
http://cuttingedgecasemods.com/