This is a horrible mess of code that generates a PDF of checks that you can print out on check paper.
To use it, edit checks.php and fill in your bank details, routing number, account number, etc. You can optionally include pay-to information as well.
There are almost certainly better ways of doing this, like using an actual program designed for this purpose. However, I've been using this code for almost 10 years now, and is for some reason the easiest way for me to print checks.
I can't find the link to the exact check paper I have, I bought like 1000 sheets a long time ago and have been working through that stock since then. I think it is this one though: http://www.amazon.com/Three-Personal-Sized-Blank-Check/dp/B002WCVW5Q
If you have a laser printer and can buy magnetic ink, the checks will work pretty much everwhere. If you print this out with a regular inkjet or laser printer, I've heard of some ATMs that don't accept them, but otherwise work as normal. These days most checks are scanned via optical methods (camera phone on mobile bank deposit, or inside ATMs), so you shouldn't have a problem with non-magnetic ink. Legally, a check doesn't have to have magnetic ink, it was just historically the best way for machines to scan the routing and account number.