A very nice little secret on Apple’s website is their refurbished. Tho its still a luxury item and the best for video editing, you can find a good deal. In fact this is where I picked up my iMac last Christmas: Certified mac
If you want the latest and greatest hardware then its no secret Newegg is the place to go. The other benefit of this site is the community. People are encouraged to leave feed back of products they buy so you can read the pros and cons. Newegg.com
Just like company stocks, computer CPU’s are traded on the open market. To give you an edge on buying CPU’s, follow their past trends: sharkyextreme.com
Another company that knows how to profit many times off a sold product is Dell. They are slowly rolling out their auction site. Yes they are older, but the prices are attractive: dellauction.com
Another site that posts good cheap used prices is: http://www.computer-show.com
If all fails you really want to roll the dice, craigslist has always had some great deals. http://craigslist.org/sys/