Verno wrote on Mar 8, 2011, 12:19:

From Steam's side, it is tied to your steam account, but you can transfer games to another account for 10 dollars I think.

Wow really? When did they start this? Do you have to be the legal owner of both accounts and if so what proof do they require? This sounds hella handy, I've got a pile of games my brother would probably love and I never touch them anymore.

Originally Posted by Arctic Ice via steam forum:
Transfer a CD-key to another account

Going past the fact that you aren't allowed to sell Steam keys/games (as outlined in the SSA) there is a small leeway.

You, in fact, can transfer a CD-key from one account to another. The process, however, has very hefty limitations and sounds quite tedious.

It might not work in your case but there are a few cases where it will work.

CD Key Reset Process