http://www.cardsdirect.com/
Pick up to 3 cards to request samples from (when you click on a card there is a "Request Sample" link under the image). Checkout like normal, no credit card required and shipping is free.(recieved)

http://www.postycards.com/page.catalog/session_id.F62CFCF114535CD44434A6614F8E0487B4CC03529D66
Browse the site and pick up to 3 cards and enter the item #s in the box on the request form.

http://www.hammond.com/info.aspx
The request page just says to enter the item #s of the cards you are interested in receiving samples for. No limits or specifications are mentioned (received 8 samples).

http://www.businessgreetings.com/hbe/
This is a division of Hallmark so the cards are more unique than many other business card sites. To order samples, just select the cards you want and click "Request a sample card" next to the pricing information. A window will pop up and ask you to enter your address and whatnot. No limits mentioned.

http://www.bestholidaycards.com/static/bhchome/index.htm
Browse their card catalog and jot down a few item #s of the ones you want samples of and mail your request to info@bestholidaycards.com with the subject line "Sample_Request". No limitations or specifications mentioned.

STOCK UP FOR THE HOLIDAYS!!HO HO HO

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