When I was young, I had a couple pen pals.  It was so much fun to receive those letters!  Letter-writing has gone to the wayside a bit, but sending a card even with a small note is sure to be treasured by the person you send it to!
For my card, I cut Premier Polar White Cardstock using the new Cross Tiles Cover Panel and adhered it to the cardbase.  Using the envelope image in the new Snail Mail set, I stamped on several colors of cardstock, diecut and popped up each of them to create a rainbow of happy mail!  The sweet little mouse from the Mouse Mail set went perfectly with the colorful envelope images.
Here are the cardstock colors I used: