I've only used https://blocktrades.us myself and it's worked great for me with zero fees between steem/steem dollars and bitcoin. The only small fee occurred between my bitcoin wallet and my bank (which has nothing to do with blocktrades.)

While the look of the site has changed a little, here is a fantastic guide to walk you through the process:
https://steemit.com/steem/@thecryptofiend/how-to-use-blocktrades-the-fastest-and-easiest-way-to-buy-and-sell-steem-sd-and-my-review-of-the-experience