Sometimes I forget how dense our version of the mythology has become…
One important safety tip: don't try to absorb it all at once. It'd probably drive you insane. I mean, since I'm the guy who wrote it and I'm insane, it might be contagious.
There isn't really a “master index” but that might not be a bad idea. But a couple things that you might find helpful to start off with:
http://www.gbtimeline.tkThis is the original Timeline, centered on the original and Extreme Ghostbusters, and far more squarely based on the actual canon of the movies, animated series, and the Now Comics material.
http://www.ectozone.com/gbnyCharacter profiles of the New York Ghostbusters in the GBOT fan fic continuity.
http://www.ghostbusters.org.ukGBUK's web site. EDIT: Hm…Like Ben said, it appears to be down right now…
http://ghostbustersff.proboards24.comA fan fic site based on the Timelines
And again, let me state it:
If it's all right with the members of GBUK, you don't have to follow any of that. Some people enjoy learning all that backstory and writing in that paradigm–other people run away screaming from it. If it makes you uncomfortable and your eyes bleed, don't worry about it.
That being said, I'm more than willing to answer any questions you might have, whether here, GBHQ, or even at my own board.