Phone Cards websites:

https://www.discall.com/cards/default.asp?
http://www.callingcardplus.com/?GTSE=GOGL2
http://www.dgtelecard.com/front.htm
http://www.click4prepaid.com
http://www.masterbell.com/index.php
http://www.justphonecards.com/ (try to enter coupon code:ND-61139) 

http://www.callingcard.com 

http://www.smartprice.com/ 

http://www.bestratescall.com 

http://calling-cards.pushline.com/

http://wcdi.com/

http://www.russianday.com/phone/