Happy Birthday Banner Card with balloons -- one of my absolute favorite card projects. I've tried it as a congratulations card too!
Flower Drawings on Watercolor Backgrounds (Spring Art Project for Kids)
Fourth of July Firework Salt Painting - Busy Mommy Media _ This is such a cool art project for kids! It looks so neat when it is done. I love that it uses stuff I already have on hand. This would be awesome for a rainy day activity!