GnuCash - A personal and small-business financial-accounting software, licensed under GNU/GPL and available for Linux, Windows, Mac OS X, BSD, and Solaris.
Checkeeper - *Have your own check stock? Awesome, Checkeeper will work with virtually any type!
Xero - Xero is online accounting for your small business.
CheckSoft - Check printing software
Scramjet.org - Serverless data computing
Online Check Writer - Online Check Writer is an all-in-one financial service provider with all kinds of payment options to pay and get paid.