Here's a cheap activity Little Bear has enjoyed. We took strips of styrofoam that came from a recent bookshelf we purchased and had to assemble. Then, we used a marker to make dots (or even letters) so that Little Bear could poke through the golf tees into the dots.
It's inexpensive and seemed to entertain Little Bear for some time. In addition, it teaches early writing skills by strengthening hand-eye coordination and fine motor skills.
Styrofoam (free) + Golf Tees ($1) = Cost of Activity: $1