I made some thank you cards this week for baby's birthday presents.
I added the words "thank you" to a photo (in Paint, who needs Photoshop?!), and got 2 printed to a 6x4 photo. Then cut the photos, and matted each one with a co-ordinating card/paper from my scraps box and added them to a cream card. I rounded the corners of the photo, background card and card before sticking it all down.
Pretty simple but a nice way to post a few thank yous and make a few people smile :-)
Note: I have learned from experience that simple means these things get done! I'm certain people would rather get a simple thank you note in the mail than not get anything at all while I plan some complicated thank you and never get around to finishing it :-)