One of my favorite things to do when I throw a shower is to make thank you cards that match the invite to give the guest of honor. Since I already have the guests' addresses on mailing labels, I just print an extra set, affix them to an envelope, and add return address labels with the guest of honor's address. That way the wife/mom-to-be only has to write the thank you notes and stick stamps on the envelopes.
These are the matching thank you cards that I made for Lisa. They are very simple.
stamp: Amuse Little Giraffe, Stampin' Up! "thank you"
ink: Impress chocolate
other: Memory Box pearl stickers daffodil