Two fan-created websites were created about the Callahan's series. The first, located at www.callahans.com, had been under construction for many years. It is now offline but can be viewed on the Internet Archive's copy.
The second was located at www.callahans.org and had been around quite a long time, linking to yet more related people, places, things, & events than the first. It went offline in 2018. The Internet Archive preserved much of it.