Heres the big question. Are they tied to your account at all?
Are any games from the Humble Bundle site at all?
If you answered yes to the 1st question, then you cannot trade the game. Its apart of Valve's EULA (End User License Agreement), which states that once you install the game onto their program, its permanently assigned to that account. No ifs, ands, or buts.
However, if you bought a game way back before Humble was able to get their ducks in a row and you could spawn Steam keys all over the place, then yes its possible to trade a game. Heck, you can download some of the games outside of Steam.
Just kindly update us.