Uplay

You copy the keys here uplay is not supported in steamgifts

Or you add someone and gift them your choice.

Make some funny event when you can choose a winner or some forum/group vote or something like that

The most frequent way I've seen done is to add them as an extra to a normal giveaway. Seems like the easiest way as well, give away some cheap bundle extra and say "this also includes blah on Uplay".

Drop them in the Orphan Key thread with something making the keys not as easy to snag as just copy-paste, to avoid the bots -- http://www.steamgifts.com/discussion/Zq0rb/drop-your-orphan-keys-here-thread-not-sure-if-key-got-used-or-desura-other-platform-keys/search?page=94

EDIT: Yeah, no. Don't do my earlier suggestion.

Orphan Key Thread would be good, or make a puzzle that leads to somewhere that has the keys.

I play uplay games I wish there was site where u could make giving always for all games from all drm loaders and direct dl. That be cool site . That why we could share all games .

You could do a www.itstoohard.com puzzle or something or a manual raffle where u get people to post in a thread and draw a name out of a hat.

I dont have time for itstoohard, maybe next time. Orphan keys here i come. BTW its Far Cry 3 Blood dragon and splinter cell chaos theory if ure interested