My suggestions:

Newegg.com - Hands down the best parts supplier I've dealt with. Great prices and in terms of timeliness the cheapest shipping has always arrived 1-2 days after I ordered it.

Microcenter - If you're lucky enough to have on in your area, they offer great deals and selection on pc hardware, but not nearly the quality issues that Fry's has.

Fry's Electronics (click here for current deals)- They offer great deals and huge selections. The problem I have with them is a HUGE difference in quality when I buy components here. As an IT consultant, there was a point where I was building a PC about every month for a client -- when using Fry's for the parts, I had about a 20% failure rate. That's horrible. In my opinion it's partially due to the fact that (at least at both in my area) when you return an item, it's often re-sealed and put right back on the shelf. The only reason I built several systems off parts from Fry's was because this client was ripping me off, so I was penny pinching to pull a better margin (immoral, i know. bad majo. they deserved it, though). I would never build a system I'd plan to rely on from Fry's parts.

PC Club - They don't always have the greatest prices, but alot of system builders I know prefer to get their local parts from these guys when they don't order from Newegg.