Short of straight up coding, what, technically, do you wish your favorite non-technical cofounder knew how to do to help you function better in your job or let you focus on the most important things. For example:
* deciphering production logs
* proficiency in vi or another editor
* rails console or similar
* reading a postfix or sendmail log
* basic git commands, reading commits
* analytics and testing
* enough HTML/CSS/JS to make content edits on a corporate homepage
* decipher server/application alerts to understand what's a real issue, what isn't