The Berlin defense 3.Nf6
The classical/cordel defense 3.Bc5
The Steinitz defense 3.d6
Bird's defense 3.Nd4
Fianchetto defense 3.g6
The Cozio defense 3.Nge7
The Schliemann Defense 3.f5
Some of these you might just want to know enough to get started. The Berlin defense you might want to know more about, although fairly rare, it's making a comeback. It's probably the most common move other than 3.a6. The cozio seems to come up a fair amount (enough anyway). The Schliemann it's probably good to know the first couple of moves. Never had it come up against me. Steinitz and classical you probably want to know a bit about but they arent that common and are fairly intuitive for white i think. Bird's is good to know what to do so it doesnt catch you off guard, but I dont think there's that much to know, and i think it's very rare.
For me I think as black I would be quite relieved to see the exchange lopez though.
So I've decided to start playing the Exchange Ruy Lopez as white (1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Bxc6).
What other third move options for black are common enough that I need to be prepared for them? Any suggestions for how to play against the major variations? As black, I've always played 3. ... a6, so I'm not really familiar with the other variations of the Ruy Lopez.
--Fromper