Thank-you notes are the final act of a birthday and an important lesson in good manners. Tackle a few at a time so it's not such a chore. And aim to send them within a couple of weeks (though parents understand if it takes a month).
* Whether they're store-bought or homemade, do add a personal element to each. A simple "Thanks for coming to my party. I really like the Polly Pocket set" is just fine. Or you can transcribe what your child says about the gift. Let her sign her name, draw a picture, or just add her red-crayon scribble.
* For a special touch, snap a photo of the guest at the party and include it in the envelope, or take a group shot and make it into a postcard -- it'll double as the note and one last party favor.