Oh my goodness, have you heard of Red Stamp? It is one of my absolute favorite iPhone apps, not to mention free!
Basically, the app gives you cute cards for different occasions, that you can personalize with your own messages and photos, and then the image of the card can be saved to your phone do that you can text or email the card to anyone.
I am obsessed, I now send cards for everything, i have even done party invitations! Here are two cards that I have done recently, for my mom on mothers day, and for my wonderful husband on our anniversary: