I've had a pretty busy month, hence the lack of recent updates, but the latest update is a pretty big one! I intend to go back to updating my coverage of the Danish/Urusov type lines next.
I have completed my coverage of the King's Gambit Accepted (there may be the odd significant line here and there that I missed out, but I think I've been pretty thorough). The main summary can be found at http://tws27.weebly.com/kings-gambit.html and there are links to illustrative games and comments for the Modern Defence, Cunningham Defence (which includes some coverage of 3...Ne7, 3...h5 and 3...Nf6 also) and the Bishop's Gambit (3.Bc4) and the Mason Gambit (3.Nc3).
My previous update summarised my feelings on the Modern Defence, which now has some games and analysis devoted to it. I think that the Modern Defence is looking fine for both sides at present.
The Cunningham Defence (1.e4 e5 2.f4 exf4 3.Nf3 Be7) is a flexible line which can be followed up by a check on h4. Following 4.Nc3 Qh4+ 5.Ke2 the chances are roughly equal, as White seems able to get away with having a centralised king in this line, and can sometimes even advance the king to e3 to support the centre. However, 4.Bc4 Qh4+ 5.Kf1 is probably inadvisable for Black as the king ends up relatively safe on f1. Black's safer option is 4...Nf6 5.e5 Ng4 which gives both sides active piece play, but with chances of an edge for White. In many lines, Black plays ...d6 and an exchange of pawns and a queen swap down the e-file follow, in which Black is left with a slightly-misplaced king on e7.
The Wagenbach Defence (3...h5) is dubious as it neglects development, but White has to know what he/she is doing. In particular, there are various lines where White has to sacrifice a piece on g5 at the right moment in order to secure an advantage. The Schallopp Defence (3...Nf6) is quite dubious, but 3...Ne7!? is probably equal in value to the Modern Defence, generally intending to follow up with 4...d5, and has the additional advantage of being less well explored.
The King's Bishop's Gambit (3.Bc4) looks fully playable. I feel that the most critical response is the relatively rare 3...Nc6 (a view also shared by Mark Morss and others at the Chesspublishing.com forum), with the idea 4.Nf3 g5 leading to a Hanstein Gambit, while 4.d4 leads to active piece play for both sides but theoretically the onus is primarily on White to prove equality. Instead, 3...Nf6 4.Nc3 c6 is the most common recommendation, leading to equal chances after 5.Bb3 d5 6.exd5 cxd5 7.d4, or 5.d4.
Tempting is the check at h4, but White's king turns out to be relatively safe on f1, while 3...d5 is well met by 4.Bxd5 which might confer a slight advantage to White. One important point behind 3.Bc4 is that 3...g5 4.h4 is dubious for Black, since 4...g4 no longer hits a knight on f3.
The Mason Gambit (3.Nc3) is rather dubious because after 3...Qh4+ 4.Ke2 White is a pawn down with a misplaced king. However, this isn't the end of the story, because White does tend to get a strong centre and attacking chances, which produces rather murky and complicated positions which offer practical chances. The traditional recommendation 4...d5 is not a serious test of the soundness of 3.Nc3, but I think that Black has good chances of a theoretical edge after 4...Ne7 and 4...Qe7, and maybe 4...d6 as well, if Black finds John Emms's suggestion of 5.Nf3 Qd8!?. Black can also try 3...Nc6, steering play towards lines that can arise via the Quaade Gambit, and here I have covered 4.d4!?, the Steinitz Gambit, which is the most consistent response for fans of the 3.Nc3 lines. I was heavily involved in a Chesspublishing.com thread questioning whether the Mason Gambit is playable, and I think the answer is definitely yes for casual and rapid games, but for slow tournament and correspondence play I have doubts.