For the inside of the card I used the photo editing (FREE) program Picnik, picnik.com. There is a wonderful tutorial to the program from iammommahearmeroar.blogspot.com here!
I had used picnik before I had photoshop but did not know its potential until I watched her tutorial! AWESOME! So I made the who, what, when, were on picnic then just printed it along with a picture of the big boy. (More projects from picnik to come!)
Notice the stamp I purchased at Joann's has two lines. I covered up the last line for the invitation. I just put tape over it, put it on the stamp pad, then took the tape off to stamp it. Each card was a little different but I think they are pretty cute!