We recently discovered this kids art activity set that is really fun and easy to do.  Basically you get sheets of clear plastic that you draw pictures on with bottles of squeeze paint.  Then you let the pictures dry (about 24 hours is a safe bet) and peel them off to stick on a window.   It's a project that everyone can participate in - and best done with supervision. 

Both my son & daughter  (ages 5 & 7) have had a lot of fun creating things for their bedroom winodws.  They work like suncatchers, but they are flexble, rubber like things that just cling to the window.  No suction cups or anything.

We've tried two different kits that have worked well - both are made by Creativity for Kids.  One is a small (5x7) sized box that comes with 5 tubes of colored paint, one tube of black and then four small blank sheets of the clear plastic.  This was our first introduction to the product and it worked great.  This set if best for making free-form creations.

The next set comes in a larger box (12 x 12) and we really liked that because it has a lot more colors to choose from as well as a lot of nifty templates that you can use for making your window art.  Lots of cute outlines of animals and flowers and shapes.  It's a nice touch to have the patterns to follow.

So if you are looking for a fun art project I'd recommend these.  The kids really like them and they are fairly simple to make.  Best for kids 5+ I'd say but it depends on the child.

Happy Crafting!