Stevedog13: That's the problem, the gift icon only appears next to a few games. None of the rest have that option.
ET3D: That's strange. There two types of steam redemption I'm familiar with on Humble. The old way is that you click the Steam key and you get a key, which you can do anything you want with. The new way is that you click the Steam key and it redeems on an account, in which case you have the gift icon. The second type has a "Steam keys will be redeemed to ..." text on the top right, the first one doesn't.
I think you can't gift Steam codes or links for individuals games you've bought via the Humble Store.