You'll hear "two thousand and twelve" (BrE, I don't know if this is used in AmE), "two thousand twelve" (AmE, never used in BrE) and "twenty twelve". I don't know if the latter is used in AmE but it's become even more prevalent since the subject of the London Olympics has been talked about so much. For some reason the "two thousand and twelve Olympics" doesn't sound as neat as the "twenty twelve Olympics" or, as it's known here, "London twenty twelve".
We didn't say the years this way in the UK until 2010 (ie we never said "twenty oh eight" etc). I have heard people using "twenty ten" - that may be because there was a film (sequel to 2001 A Space Odyssey) by the same name and that was officially referred to as "twenty ten". I don't think "twenty eleven" was as popular though.






