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As I have mentioned in other threads, I have used bitmixer.io many times and like their service a lot. The total approximate fees vary between about 0.6% and 1.0%, you can to a degree set them yourself. Although I am not an expert, the taint analyses have done seem to show that bitmixer does hide quite well the original sending wallet and the receiving wallet.
I am in their signature campaign because I am a happy customer. I have not used exchanges nor casinos for mixing coins, so cannot comment.
===> Follow their instructions carefully! <===* * *
SharedCoin (from blockchain.info) is an easy to use service whose feels are roughly the same: under 1%, although they offer an option to eliminate most of the fee. IMO, each of us using SharedCoin ought to just pony up the 0.5% - 1.% random fee to encourage blockchain.info to continue to offer the service.
The algorithms of the two appear to be different. For the extra-paranoid, try using both services in sequence...