I was recently introduced to the free Red Stamp app via Pinterest and I LOVE IT. It's such a cute way to send a quick note or message to somebody, especially personalized thank you notes for gifts for your baby.
The app isn't just for thank you notes. You can also send notes of congratulations or quick hellos. These can be sent electronically (free) or through the mail ($2 for 1, but the price goes down to $1 if you want to send a lot).
I wish I had this when Selah was born for quick thank you notes for meals dropped off or gifts mailed (before I forgot to send them in a timely manner). I'll definitely use this with the next.
Go get it now. You'll love it even if you don't need it for kid's thank you notes. :)