I started out with counselling, thought not just about the affair, more about the feelings of low self-worth that it triggered in me. That was really useful, though. But really, as others have said, it has just taken time. Three and a half years for me now and I still have the odd moment of rage when he reminds me of what a twat he was, but it has just got less and less frequent, very gradually.
I think one reason the counselling was good is that it gave me the idea that in fact the breakup could improve my life in many ways. And after this time I do still feel like it was a turning point which has left my life richer and more "real" as I now take less shit from people, have got over some of my hangups through counselling and treatment for depression, and am thus more active about going out and doing things, making friends etc. And I realise that the relationship with my ex was quite restrictive in many ways and I now have new opportunities. I also don't see the OW as having come out on top; in fact I feel sorry for her as she is bound to have the same problems with my ex if they have children.
My lovely dad has Aspergers and met up with my ex last time he was here "because he missed him", and because he does not understand what he did. As far as I can tell he thinks I just misread the situation and imagined the affair, when actually I had firm evidence for my ex going to a sex hotel, on holidays, dissing me and the kids, etc. I'm learning that you can't make other people see things your way, and the frustration at that is gradually waning.
It sounds like you don't see any silver lining, which is bound to make the anger last longer. Are there any positive aspects to him no longer being there? Anything you've always wanted to do, and can now do?