Best place to buy parts?

Amazon. Fantastic return policy (turned around a bad MB in 2 days with prime).
Microcenter for processors - great price but usually in-store if you have one near you.
FrozenCPU - mixed reviews but I have had no problems with fans, etc.

NOT newegg or Frys - newegg quality and prices have tanked and Fry's prices aren't good and their retail stores make you feel like a criminal.

Ones that look interesting but haven't tried yet:

jab-tech
performance-pcs.com
coolerguys
mnpctech for case mods

GeneO said:

Amazon. Fantastic return policy (turned around a bad MB in 2 days with prime).
Microcenter for processors - great price but usually in-store if you have one near you.
FrozenCPU - mixed reviews but I have had no problems with fans, etc.

NOT newegg or Frys - newegg quality and prices have tanked and Fry's prices aren't good and their retail stores make you feel like a criminal.

Ones that look interesting but haven't tried yet:

jab-tech
performance-pcs.com
coolerguys
mnpctech for case mods

GeneO:

I have had good luck with jab-tech for small parts, including fans. They are in Oklahoma.

Also---Koolertek for fans. They are in Brady, Texas, but don't carry much other than fans and heatsinks.

Some of the parts sources are cheap on parts, but high on shipping---so you have to pay attention to the overall price.