You can also try Craigslist. I've had success there. If you don't want to meet in person, there are people that don't mind paying by paypal and having you ship... Actually I get more offers to ship then to meet up.
Makeup Alley has a swap program...you can post items you have to trade-- then you can contact members (or they can contact you) about swapping for something they have. Some members swap used items but you can specify that you only want to swap for new things.
I use makeupalley religiously to swap makeup that doesn't work for me. I have saved so much from doing this! They also have an amazing database for product reviews (which has also saved me money/dissapointment lol).