Take a look at mixing services[1], which seek to do exactly that.
Re:Tor and HTTPS
by dave1010uk on Monday June 10, 2013 @02:56AM
(#5852825)
I've heard that SatoshiDice is used for this. It's technically a gambling site but you can set the odds so you have a 98% chance of winning.
If not there should be. You send X amount of bitcoins to a middle man who then gives you X amount back. Technically they will be different coins and they'll go to a different account #, so you can't trace anything.