You think it's hard in Knoxville? Try finding a partner in Kingsport, where I live.
I've heard some people have had success with polymatchmaker. I think some people have met people through repeated CL ads, too. And have you tried attending any of the swingers' parties in Knoxville that are listed on swinglifestyle? Even though swingers normally don't get into polyamory, you'll find a huge variety of lifestyles at those parties.