If Nc6, Nf3 keeps the ball rolling like a knight gambit
Kings gambit accepted bishops gambit variation

ChessBase Online has 4059 games after 3.Bc4. That database does not include the 154 games in my personal database of online games. I've played both sides of this position, but more often White. White scores 69.9% in my database.
3...Nc6 is the fifth most popular move in CB Online. 3...d5 gives Black the best results, statistically speaking.
Tony Kosten is the highest rated player who has employed 3...Nc6. 3...Nf6, 3...d5, nd 3...Qh4+ are all preferred by the top players.

Polgar used to play the king's gambit really well:
But it was a different time then. Maybe the gambit can be redeemed but we have to remind ourselves that she probably gave it up for a good reason, a reason other than the Ruy is safer with richer strategic value.
Just a small information about The King's Bishop Gambit.
If you want to learn it you might want to try to get your hands on the book 'The Fascinating King's Gambit' by Thomas Johansson which covers a full repetoire based on the 3.Bc4.
About 3 ... Nc6. This move is also considered as the refutation by
GM John Shaw in his book published lately, and in fact the lines covered there in my opinion come close to a real refutation.
A small sidenote: 3 ... Nc6 is also Houdini 3's choice after very long analysis ending with an advantage > 0,5 for Black, though as always engine evaluations are not the one and only truth.
Recently, I have been playing the king's gambit exclusively as white. The gambit starts out with e4 e5 f4. Normally Black accepts the gambit and plays exf4. I play a very aggresive move Bc4! This is called the bishops gambit derived from the kings gambt. Since these sequence of moves have only been played 707 times according to the database on chesstempo.com you can see the unpopularity towards the king's gambit accepted bishops variation. Unfortuantely, there are very little chess masters who explain all the information you want to recieve in any opening. For example, theory, common plans, and common things to look for. So basically the only way I know of to gain knowledge about this opening is to learn the variations. Fortunately, there are only 3 responses to 2 Bc4 that have been played over 50 times says chesstempo.com's database. The 3 responses in order of most popular are Nf6,d5, and Qh4+. I have studied each variation give or take 8 moves. My friend knows openings like the back of his hand. He believes he knows a refutation on move 3. His "refutation" is e4 e5 f4 exf4 Bc4 Nc6.I can't really disagree with him because I have no way to prove him wrong. I would be delighted if a strong player can prove his refutation wrong. I would also be delighted if anyone could find me a website, video, or a knowledgable person to inform me. As always every comment is highly appreciate. Below is a correspondence game where I dominated using this gambit. Thanks for reading everyone!
P.S. If there is a refutation after 10 moves or so chances of a player my strength 1400-1600 knowing the refutaion I would say are 1 in 1000. On the other hand, If there Nc6 happens to be a legitimat refutation then I might think twice before choosing this gambit.
http://www.chess.com/echess/game?id=74166796