This is usually called the Halloween Attack -

-see this page for a database of games

-see this page for some more classical games in the Halloween Attack

-Tim Krabbe's experience with the Halloween Attack

Also known as the Schultze-Müller Gambit, I believe that black theoretically is much better after the knight sac, but proving it is quite another story. The above links might help.

I'm not a chess pro so I could be wrong, but you could play:

2. d7-d6  This wouldn't be that great because you wouldn't have any light or heavy pieces active while he could than take out another light piece and become active, but it would be good for pawn structure.

2. Nf6  This would offer an exchange leaving with you with equal positions, after his next move you would decide what to do.

2. d7-d5 I wouldn't do this just because i wouldn't like making my queen so active, but it is an option. To be honest though I wouldn't do this I would choose something else.

Another thing also is that you may want to bring out your queen to f6 to defend, but again I don't like wasting a turn on bringing out the queen in the opening. Generally I don't like moving my queen out in the beginning because your opponent can threaten it causing you to move it twice which is never good.

You can also bring your bishop to d6 to defend but than you compromise your pawn structure.

To conclude: I'm not a pro so I can't tell you an opening to counter this, but since there is a lack of response I could only give you my own view on it. I personally don't move both my knights out unless it's a productive move in someway. Id rather move my bishop to threaten or cover ground in some way or a good pawn move. Sometimes all you can do if you don't know openings is exchange and try to play your best and just roll with the punches so to speak.

Also: Try to view one move ahead itleast, in this example you showed than you know your going to have to move your knight TWICE in the opening, so instead make a move that would exchange pieces or defend in a way that would make a bishop or pawn active. As a general rule never make a move in the opening that will make you move your piece twice(thats a rule with few exceptions).

Qc6

You shouldn't open with that. Maybe using the queen to Qc6 and then capture the pawn.