This is a listing of over 500 companies (past and present) that design and/or publish role-playing game products. The listings include links to my RPG Encyclopedia for each RPG that the company produced. The encyclopedia in turn includes links back to this lists for the company for each RPG entry. The listings also include as much contact information and other background that I gather about each company. Please note that any of the information is liable to be out of date. When there is no web page, the listed addresses, phone numbers, or email for a company may be what is printed in gamebooks which were published several years ago. If you have any additional information, please email me at jhkim-at-darkshire-dot-net.
There are, of course, plenty of other sources for this sort of information. The sources I know of are either less complete or provide less information.