I have updated/expanded my coverage of the Staunton Gambit (1.d4 f5 2.e4, which I have played occasionally in casual games) with analysis of three illustrative games which contain notes on the various deviations for both sides.
This can be seen as a sounder relative of the Blackmar-Diemer Gambit (1.d4 d5 2.e4) since 1...f5 weakens the kingside and does not develop anything. However, after 2...dxe4 3.Nc3 Nf6, White should start by putting pressure on the f6-knight with 4.Bg5 (which was Staunton's original preference) waiting for a better moment to play f2-f3. White does indeed get an improved version of the Blackmar-Diemer after 4.f3 exf3?! 5.Nxf3, but 4...d5! gives Black easy development, envisaging ...Nc6, ...Bf5, ...Qd7 and ...0-0-0, and if anything is probably less sound for White than the Blackmar-Diemer.
After 4.Bg5, most critical is 4...Nc6 since, for example, 4...g6 and 4...c6 are well met by 5.f3, and Black does not get the easy development plan that arises after 4.f3 d5, and White consequently gets sufficient compensation for the pawn, even if Black hits out in the centre with 5...d5.
Of particular importance is the third game, A. Bezemer - H. Froeyman, played in 2013, in the exchange sacrifice line with 5.d5 Ne5 6.Qe2 c6 7.0-0-0 Nxd5 8.Nxd5 Nf7 9.Nf4 Nxg5 10.Qh5+ Nf7 11.Bc4 g6 12.Bxf7+ Kxf7 13.Nxg6 hxg6 14.Qxh8. At first sight, Black doesn't appear to have much, but in fact Black has sufficient compensation for the exchange because of White's undefended queenside, which can quickly be attacked with ...Qa5 and ...Bg7 before White gets the chance to work up an attack on the black king or consolidate the material advantage.
There is also an interesting discussion of the line at http://chess-brabo.blogspot.be/2013/10/iccf.html The main downside of this line is that, if played accurately, it is hard for either side to avoid draws by perpetual check.
But the whole line with 4.Bg5 Nc6 5.d5 Ne5 6.Qe2 still offers interesting and equal play (from both sides' point of view) for both sides have reasonable deviations. White's most promising deviation is probably at move 9 with 9.Nh3, while Black can consider 6...Nf7 or 6...d6. In conclusion, the Staunton Gambit is less likely to give White a theoretical edge than the positional main lines against the Dutch Defence with c2-c4, but it appears to be fully sound and is pretty dangerous. At the same time, it does not prevent Black from getting the sort of tactical, attacking/counterattacking play that attracts many players to the Dutch. I think the main reason why it doesn't score as well for White in databases as the Blackmar-Diemer is because it has gained more support at grandmaster level, where such gambits are often less effective than at club level, and most repertoire books tend to cover the line from Black's point of view. At club level I see no reason why the Staunton Gambit shouldn't score very highly in the hands of a player who knows what he/she is doing.
In the meantime I have done minor updates to the Danish and Urusov Gambit coverage to reflect recent discussions on those openings with Mark Nieuweboer. In the critical Urusov Gambit line with 1.e4 e5 2.Bc4 Nf6 3.d4 exd4 4.Nf3 Nxe4 5.Qxd4 Nf6 6.Nc3 Nc6 7.Qh4 Bb4, it seems that White can continue with the standard 8.0-0 Bxc3 9.bxc3, and if 9...0-0, then his suggestion 10.Re1 looks pretty good, saving a tempo with the c1-bishop compared with 10.Bg5 h6 11.Bxh6 which leaves White with some problems proving full compensation for the sacrificed bishop.