three years of my work-life was spent as a preschool teacher. part of the job was to come up with inexpensive but stimulating activities for the kids, and this is one of the easiest and cheapest, but also one that the kids loved the most.
my little guy is finally old enough to start enjoying this little activity, and i can't tell you how nice it is to sit him in his high chair and have him play quietly while i make dinner! the best part is that i know he's discovering and learning as he explores texture, colors, and cause-and-effect.
plastic bag that seals tightly at the top (like a Ziploc bag)
paint (I used Crayola's washable finger paint)
just dot little bits of paint in the plastic bag, close the bag, getting out most of the air, and tape the top closed with packing tape so the bag can't be opened. if your kids are anything like my little guy, that bag will be opened in seconds with paint everywhere, so make sure you tape it closed!
really, it's so simple, but can give lots and lots of entertainment and exploration.
i even gave my son a block, crayon, and cars to run over the plastic bag so he could see the different effects. he loved it.
other things that i've put in the plastic bags using the same method are:
+ white shaving cream (just the cheap stuff from the dollar store) and food coloring
+ cheap hair gel (and you can add buttons, beads, and little toys for even more fun)
+ baby oil, water, and food coloring or glitter
really, anything goes, so be creative with it and have fun!