I think the below list of people are really 'bookworthy' to anyone interested in the history of Scientology, if any of them could or would talk. However it appears that most of them are, or probably are, under either a non-disclosure agreements aka 'gag orders or not willing to speak up further or at all.
1)
Pat Broeker as mentioned earlier in the thread : Life with Hubbard from his perspective - as opposed to claims about him made by others in lieu of him being unable to speak for himself.
2)
Alexis Connelly aka Alexis Valerie Hubbard Hollister , Hubbard's other daughter telling, of her knowledge and perspective on things ( including some revealing of the tell all tapes her mother
Sara Northrup Hollister made before her death and provided in whole or part to Lawrence Wright, as mentioned and quoted in his book, 'Going Clear'
3)
Terri Peter Gillham Jr. Gillham Gamboa, Janice Gillham Grady - children of Peter Gillham and Yvonne Gillham Jentzsch, and stepchildren of Heber Jentzsch: on all their life adventures and misadventures before and during their time in the Sea Org and working for Hubbard, life growing up in the Gillham household and of course, any info on Hubbard's dirty deeds yet to be revealed
4)
Michael Meisner at one time of Guardian's Office, who is probably in the federal witness program to this day, if he's still alive. It would be nice to hear what he has to say about the Guardian's Office, the things he did for them, the consequences of going to the FBI and reporting the crimes (
Operation Snow White,
Operation Freakout and then and now.
Other refs:
http://lisatrust.freewinds.be/scientology/snow-white/index.html
http://www.cs.cmu.edu/~dst/Library/Shelf/miller/bfm21.htm
http://www.xenutv.com/blog/index.php?s=meisner
Oops, forgot to add for all the obvious reasons:
5)
David Mayo and Julie Mayo