A question

An answer

give them away on the forums

Somewhere else.

This site is only for Steam keys. We have no way to authenticate that giveaways off Steam actually happen, so it's problematic to have off-Steam giveaways because it is impossible to verify, so people could fake giveaways for contributor value.

You can only giveaway Steam keys/gifts but you can drop the keys in the forums. There is no bonus for you if you do so, just warm feeling of being generous ;)

From Guidelines:
All giveaways should be for Steam redeemable gifts or Steam redeemable keys.

Edit: http://www.steamgifts.com/discussion/Zq0rb/drop-your-orphan-keys-here-thread-not-sure-if-key-got-used-or-desura-other-platform-keys-part2

You can only giveaway Steam gifts/keys.

You can also make a forum giveaway, but that won't count in your CV.