My four-year-old LOVES workbooks. After dropping $1.99 on a flimsy Dora edition, I started snapping them up at yard sales for under a quarter. Most have a little "preowned" scribbling, but they're still cheaper than printing sheets from the Internet. It makes for a hodge podge of workbooks, though! To add variety to our days, I tore a few sheets from each book and placed them inside a five-cent pocket portfolio. Each day has its own folder, with pages from each workbook. I've found this way of recycling old workbooks cuts the clutter considerably!
**I know the more frugal moms would insert each page into wipeable clear plastic page protectors, but Andrew and I have a bad history with dry erase markers.