Going through the files and found my official International Ghost Hunters Society I.D. from 1998.
I couldn't find a website for them (and don't remember how it came to be I found them and sent away for membership) but I did find this link on Amazon for International Ghost Hunters Society Home Study Course by Dave Oester. You can read it on Kindle for free (I downloaded it) or buy a paperback version for $9.95.