Hardware Store Chess Set by jsuits.
Angry Peeps Game. Because you still have Peeps left from last Easter.
Quick & easy slate tic-tac-toe board.
Speaking of tic-tac-toe, how about this to-go version using dinosaurs? Rrarr.
Alter some regular old squirt guns into sweet rubber band guns.
Slotted paper animal toys - cheap, simple, easy. And will entertain your kid for at least 20 minutes.
Wooden paper slingshot. Make it out of junk mail for bonus earthkarma points.
Marshmallow blow gun made from PVC pipe.
Wheelie duck on a stick toy - made from stuff from the recycling bin.
Heart-shaped memory game made from gift wrap and recycled cardboard.
DIY Parachute guy - remember those?