I've tried various techniques, just to create enough sets of pieces to give to a few people. I tried ordering a set of plastic pieces from Canal Plastics, and that was great, but just too expensive to get more than a single one of each piece. The standard set I'm currently thinking of has 11 different types of pieces (with the option to haul out the scissors and construction paper and make more). I tried casting the Canal Plastics pieces into silicone molds and making urethane positives, but that turned out to be a mess, with poorly shaped pieces, all bubbly and ugly-looking.
The method I use now is to cut mat-board with straight-edge and razor. It works very nicely, but is slow, and there's the risk of blood.
Fortunately, when all you want is a bunch of squares and rectangles cut out of thick card stock, it turns out the best place to go is a printer, someplace that makes business cards. So after Googling around a bit, I've found a few places that seem enthusiastic, and who hopefully will start making bids on who'll get to produce enough pieces for 250 full sets. That will more than satisfy current demand, and give a nice cushion besides.
Hopefully in the next week or two I'll have some actual sets available, and then the folks who've been asking for them will hopefully start showing their friends, who will want sets of their own. Nothing beats a business plan that starts with creating something great that lots of people will love.