Hardware (general):

• pricewatch
• lwn
• The Register
• Tom's Hardware
• Ace's Hardware
• sysopt (hardware reviews and guides)
• ChipGeek (comprehensive CPU and chipset specs)
• iXBT hardware
• AnandTech
• SharkyExtreme, weekly CPU prices
• System Logic
• Linux hardware compatibility HowTo
• RedHat hardware compatibility Lists
• Hardware sellers ratings