I have done some work previously on the problem and came up with a (theoretical) solution that is quite analogous to CoinJoin but that uses a fixed network off 2-party txs instead of a potentially bigger one. You can see the video here
http://www.youtube.com/watch?v=6hc8qaR_Fok&list=PLUOP0P68GJ3BGjfqoLLnzAefk3ZzXQtJ7&index=35
but as there is a lot of what I am talking about that has already been discussed here, I would like to simply upload the pdf. Is there a website similar to pastebin where I can do that for pdfs? I also have a more detailed description of the network that might be of interest here that is also in pdf format.

Someone previously proposed using Secure Multiparty Computing before to implement CJ, but one must realise that SMC is only a set of tools. E.Z.Yang proposed one specific implementation using sorting, which is a cool idea, but according to Yang himself is currently not feasible in practice. In his own words, "The big obstacle is that secure multiparty sorting is somewhat difficult to implement with large keys (since integer comparison operations tend to only handle a few bits at a time)." The hunt is still on to find an efficient way to use SMC to solve the problem.

I am quite excited that people are working on making this work and will be trying the programs proposed here when I can.

Edit:
Link to the video's pdf: https://www.dropbox.com/s/nvkvo1dl3xif87v/PresentationBitcoin2013.pdf