I've been busy settling into my new life and job at Exeter recently, so it's been a while without any updates, but I've finally got around to updating my coverage of the Quaade (1.e4 e5 2.f4 exf4 3.Nf3 g5 4.Nc3) and Rosentreter (4.d4) Gambits. The Quaade and Rosentreter approaches are discussed here:
I have also provided a separate page with discussion of the "Vienna Gambit" lines that arise from 1.e4 e5 2.f4 exf4 3.Nf3 g5 4.Nc3 Nc6, where instead of playing 5.g3, White plays 5.d4 (the Pierce Gambit) or 5.h4 g4 6.Ng5 (the Hamppe-Allgaier Gambit). Note that John Shaw does not cover either of these lines in his book on the King's Gambit.
The more usual move-order into those lines is 1.e4 e5 2.Nc3 Nc6 3.f4 exf4 4.Nf3 g5, which is why I have labelled them as part of the Vienna Gambit. If you use that move-order you have to be ready for 2...Nf6 intending 3.f4 d5 (but not 3...exf4?!, since 4.e5 leaves the f6-knight without a good retreat square). Michael Goeller's sadly-discontinued Kenilworthian blog has a discussion on the line ending in 3.f4 d5 for those who are interested.
http://kenilworthian.blogspot.co.uk/ (scroll down past the most recent article and there are a few posts on that Vienna Gambit declined line).
My opinion of most of the lines hasn't changed much since reading through John Shaw's book, but unfortunately he makes quite a strong case against the piece sacrifice line 4.d4 g4 5.Bxf4 gxf3 6.Qxf3 (6...Nc6 being the main antidote, counterattacking against d4, and if 7.Bc4 threatening sacrifices on f7, his suggestion 7...Qh4+ looks good). I am also less convinced by White's compensation after 4.d4 g4 5.Ne5 Qh4+ 6.g3 fxg3 7.Qxg4 Qxg4 8.Nxg4 than in the analogous line starting with 4.Nc3. However, to my mind the 4.Nc3 lines are currently holding up well.
One important line that I have not yet got around to looking at is the Fischer Defence (3...d6 intending 4...g5). In my previous coverage I lumped this and the Becker Defence (3...h6) together with 3...g5, but for my updated coverage I plan to cover them separately (probably sharing the same section) because 3...d6 is particularly important and I need to examine Brabo's coverage of the line as it will probably improve on my earlier analysis.