Let's see, Doctor who went to Vortis: First (of course): The Web Planet, Lair of Zarbi Supremo, The Lost Ones, Prisoners of Time, etc. Second: Twilight of the Gods Fourth: The Naked Flame (comic) not sure there were Zarbi in it though Fifth: Return to the Web Planet (audio)
Zarbi have further appeared with: Three: cameo in The Mind of Evil (doesn't really count, but there it is as a memory that terrifies the Doctor)
On a side note, I've been working on a sort of "Extracanonical Daleks" sourcebook I've tentatively called "The Time Agents Guide to the Dalek Empire". I'm doing some paid writing work at the moment so it's an on-off project, but if there's anything I can contribute I'd love to help. I've already statted up pretty much everything from the Daleks various comic strips and audio appearences :-)
The Time Agents Guide to the Dalek Empire is still in production, now including information on the Skaro Degradations from George Mann's excellent novel of the War Doctor, Engines of War. At some point I'm going need help formatting it to match the other extracanonical sourcebooks. Are there templates I can use for this?
6th is a bit far off as these things go, but I have no problem whatsoever with receiving material well ahead of time, if that's all you're comfortable with. I certainly wouldn't want you to lose your momentum because the book you're interested in won't start production for another year.
But there are ways around that. I take each book as an occasion to do research on material I haven't read or listened to yet; I don't just take on the stuff I've already experienced. 4th is close to complete anyway, so maybe look into 5th Doc stuff you find interesting, and let's meet up in that thread when you have your book.
Haha, we all have our favorites and not so favorites. 5 is actually pretty great in the audios. A lot of crap in his novels though (they were cheapest on the secondary market so I scored a lot of them early on).
Well we don't cover stories as such (like the official sourcebooks), merely material from each story. When the Doctors are split up (like The Sirens of Time, or Wolfsbane), material from their bits go in their books. When they're working together, a choice is made as to where we are in his personal time line. For example, the clue to when The Light at the End takes place is where the Master is in his timeline.
I think the next instance we have is The Four Doctors (the Big Finish audio, not to be confused with Four Doctors the mini-series from Titan Comics). It features the 5th, 6th, 7th and 8th Doctors working together, so I guess we'll be looking to place it at the most suitable point in the Doctor's timeline. I don't recall there being much of an indication in the story to use as guidance. Do we then place it in the oldest Doctor's timeline (in this case, the 8th Doctor), in line with the placement of TV stories like The Three Doctors and The Day of the Doctor?