I’ve built up a nice supply of guitar chord charts that I use in my articles (and I continue to add more). I had a hard time finding any guitar chord charts online that were free to use for any purpose and easy to access.
I created these in Microsoft Paint and Pixlr and anyone can use them for any purpose (personal or commercial). I’m making them available under the Creative Commons Attribution (CC-BY) 4.0 License. That means you can use them, change them, and even sell them, as long as you disclose that they were created by soundgoblin.com (and preferably link to this page) and reference the license.