Do you have a dumpster a yard sale or a thrift store near your house???
Do you want to keep a handful of kids busy and get a project or two done while you are at it?Do you have an "oops" section at your local hardware store paint department?Do you have a swatch of upholstery fabric lying around?
We summoned up a couple helper friends and painted up a storm. Carianne painted a wooden crate I picked up for $5 at Jo-ann's craft while her younger brother, David, and my Max helped paint the chair I found on the side of the road (read about that here). Just make sure the kiddos have small brushes and you'll need to be on the lookout for big drip marks.
You have to get in the frame of mind to just let them go for it. After they finish, you can go over it yourself and give it a good finishing coat.
I used paint that I found at Home Depot for $5 for the gallon (oops paint) and a sample swatch of fabric that I picked up at a going out of business sale at Storehouse. Check your local furniture/reupholstering stores for old out of date sample swatches. Mine cost me $2, but many times they are free.
The point of this is not to get them painting something completely random and clutter-y but something useful and practical. Think about painting projects you already want to do and just get the kids involved somehow.
COST: depends on how much you have around the house...
VARIATIONS: Check behind your local thrift store for things they are throwing away. I found a sewing machine table there once. free. Also, you could do something more simple, like a frame or a small wooden box. If you are painting a room, don't make your kids stay out. Just give them a very small brush and their own very small cup of paint. Lay major drop cloths down, but let them in on the fun. Encourage them to help with your projects.