you can get free cards from vistaprint.com
basically you only pay for shipping and allow them to have there name on the back i think..
or you can get cards designed at overnightprints.com for less than 40 bucks shipping included and you get 100 i believe. you can upload your own design or use there online design program.
personally i've used overnightprints about 3 times in the past and the quality of there work is pretty good, that and there pretty fast when it comes to shipping