Last year I tried http://www.overnightprints.com/. The business cards were my design, fantastic colors, glossy, thick, calendar on the back, UV coated, and 2000 were $89. I go to re-order this year and everything was right there on the website from my previous order.
The whole process was very easy and my emailed questions about changes were handled quickly. This place is not for someone who wants to just phone an order in though as they only accept orders through their design cards pages online.

Disclaimer: I neither own nor have any financial interest in this company.
What other national companies have you had success with for business cards?
Some already mentioned sources on Jim Lee's blog may be found at:
http://activerain.com/blogsview/Great-source-for-printing?6814
Other interesting AR business card blogs may be found at:
http://activerain.com/action/search/search_results?searchfields=blogs&search=business+cards
Thanks!
Rob Lang, ePro, GRI Realtor®
Realty Executives, Hedges Real Estate
300 Rockfence Pl, Lawrence, KS 66049
785-393-2274 (cell) 785-542-1661 (fax)
rob@LetRobDoIt.com (same website name if you want to visit)

Rob,
vistaprint, it is the best place to get quality and very very cheap prices, I got 500 glossy, thick for 4 or 5 dollares, do not remember, my wife always order them for me
Ray Saenz
I use http://www.colorforrealestate.com/ for business cards. They print two sides and I include this quote on the back:
F.D. Roosevelt: "Real estate cannot be lost or stolen, nor can it be carried away. Purchased with common sense, paid for in full, and managed with reasonable care, it is about the safest investment in the world."
I have flyers and post cards printed at:
http://www.xpressdocs.com/
You can set up your own account by adding your brokerage franchise nam to the URL:
www.xpressdocs.com/kellerwilliams
http://www.xpressdocs.com/prudential
http://www.xpressdocs.com/coldwellbanker
If you order by 3:00 pm they fedex for deliver the next day! How's that for F-A-S-T?