This is a good question. I have to strongly disagree with Nelly on this one.
I did it unconsciously (adverb) = I did it without conscious effort, I did it without realising or I did it without thinking about it.
To be unconscious (adjective) = to have passed out, to be in a coma, (to be asleep).
In British English I haven't heard people use - I did it subconsciously - in the meaning of without conscious effort or in any other context.
In my opinion we an talk about our subconscious to describe the deep emotional reactions and psychological traits that people manifest through their actions.
I would be interested in hearing other people's ideas on this last point...