Printing Recommendations
I'd recommend using the thickest cardstock you can as paper weight really makes a difference. So that will depend on the printer you use. Most print shops (like Kinkos, Office Max, Staples, etc) stock a variety of cardstock but usually can handle slightly heavier paper than they have in stock. So if that's the case, I'd recommend supplying your own paper (you can buy heavy cardstock online or many craft stores carry it) and having them print it for you.