With just your home computer, standard 8.5x11" paper and Microsoft Powerpoint you can create fast and easy cards. You can use photos and graphics off the web as long as you don't market your cards*. I like putting a big design on the front and a tiny design on the back of the card. Just print cards, fold them in half twice, and you're done!
*Note: If you profit in any way from your cards or use them commercially, using someone else's artwork is copyright infringement.