Well, 31 Oct is the 20th anniversary of the 1st meeting of the CD-ROM Ad Hoc Advisory committee (some have called this the High Sierra Group), which produced the High Sierra Group Proposal, the seed of ISO 9660, which seems to have had a significant impact.
My notes show that the following organizations were represented at more than one meeting:
Apple
Digital Equipment Corporation
Hitachi
Microware
Microsoft
Philips
Reference Technology
3M
Sony
TMS
Videotools
Xebec
Yelick, Inc.