I've wondered the same thing recently, but I haven't found the time to really pursue it. I'm classified as a "caretaker" but I am the primary grower, my wife being the card holder (the grow is in her name to keep things simple, since its done here at the house).
There was a website that called itself "OMMP Pay it Forward" -- the url =
http://freemygreenpdx.com/
...I haven't been there in a while, but there might still be some venues there for trades or gifts. Another place to look might be
MeetUps, I think there are some MM ones, although I've never attended one.
As far as legal goes, I'm not a lawyer or an expert, but it is my understanding that you can give it away (or trade), as long as the amounts are within the legal quantities that you and the recipient are allowed to have. There are some folks on here who are much more precise in their understanding of the law, so hopefully someone will clarify.
CL is too random for me. I've bought and sold things through CL, and you just never know who's going to show up, so personally I'd look for a different route.