If you want to do better than "copy paper" you could run heavier stock paper through a color laser printer.
In my poor, college days, I would have entertained chopping a manila folder to Letter size and running it through the straight-feeder of a Color Laser-jet.
I literally just printed on 220gsm card in a laser printer's feed tray today. Worked great.
Before I had a pack of card, I was indeed cutting up manila folders. I only had ugly colours (that's a rule for manila folders, apparently) so it wasn't ideal, but it worked well in a structural sense for what I was up to.
Does anyone have tips for this? What cardstock should I use? Is there a particular weight that is best suited for projects like this?