I just gave mine away on Tumblr. Made a post, listed the ones that I had (brand, size, color, level of wear) and said that I would be sending them at no cost to transmen who could otherwise not afford them. I used as many tags as I could think of that people might look at, and I also posted to a few trans-related submission blogs.
I had 3 to give away and got over 100 messages about them. I looked at everyone's blogs, chatted back and forth with a few people, and found 3 folks that seemed like they could really benefit from them. I mailed two off and the other guy was actually local, so I met up and gave him his in person.
I was still recovering when I did all that, so I had some free time to kill. If you don't, I second taking them to someone local. I know the center I get my hormones from will accept donations.