The other day I was watching, "The Nate Berkus Show". If you don't know, I'm in love with his ideas. He has great ideas that are pretty easy for the average person to do. He's not one of those hoity-toity designers where everything is couture...he's normal and warm and inviting.
One of the ideas shared on his show by a guest (a celebrity contractor) was using a fabric shower curtain to recover seats for chairs. Simply remove the pad, and either using the foam provided or new foam, make a template on some butcher paper of the size of fabric that you need to cut. Remember that you need enough to easily fold over and secure. Once you have a template you're happy with, cut out the fabric from the shower curtain and attach it to your chairs, securing it using a staple gun. One shower curtain should do a minimum of 4 cushions, and you might just be able to get 6 if you're careful in your cutting!
Shower curtains are fairly durable, stain resistant, and easily affordable. Enjoy!