This pawn sacrifice is something to throw black off of the harmless path of 3.d3. The Urusoff Gambit was invented by Sergey Urusoff, a strong Russian player. The gambit begins 1. e4 e5 2. Bc4 Nf6 3. d4!? The games in this collection are here to study the positions resulting from the Urusoff and how play should proceed. The games in this collection are not shy of allowing a transposition to the Max Lange attack. However, no Max Lange attack games are in this strictly Urusoff Gambit collection.
Below are links to websites discussing the gambit.
http://www.rci.rutgers.edu/~goeller...
http://www.chesscafe.com/text/kibit...
Here's a game I just played today showing that the Urusoff gambit can be very tricky if your opponent is not versed in the lines:
1. e4 e5 2. Bc4 Nf6 3. d4 Nxe4 4. dxe5 d6?
5. Qd5! (resigns)