Do a search on Rackmounts Etc. You can also buy from Ebay and get good deals, but have to be careful there for obvious reasons.
AYKsolutions.com - High Bandwidth Specialists - 100TB/1Gbps/10Gbps Unmetered/CDN/DDOS Protected Over 20 Global Locations - Asia, Mexico, Brazil, Australia, US, CA, EU - Bare Metal and Virtual Cloud. All Managed. View our current Specials. We are Professional. Painless. Polite.
RME would be a good place to start. Same with NewEgg, which were both just suggested. I've talked with the owner of RME (that slacker!) a few times, and will be going to him when I'm ready to purchase hardware.
Douglas Hazard - Certifiable Sports Junkie and Sports Community Enthusiast
Host of Two Cents Radio - Follow @TwoCentsRadio on Twitter (@BearlyDoug on Twitter)