I feel your pain. Whilst I am still (only just) with my DH I found out about his affair with OW last summer. It happened a few years ago but like you, I'm consumed with anger. I found out where she worked,, where she lived and wanted to go around and confront her. I sent several emails which I think scared the shit out of her. I read messages between her and DH in which she mocked me and joked about the fact that she shouldn't be having sex with my husband but she liked to live dangerously which made me see red.
I wrote a (very polite/formal) letter to her setting out that I knew where she lived (and worked as sent to her work email) and that I had found evidence of her adultery and that I was in the process of drafting a petition based upon that adultery and she would be named as the co-respondent and I'd be seeking and order for costs from her. I mentioned her husband and son's names and made it clear I knew where she lived and the papers would be served on her there.
I also commented that if she liked to live dangerously, she should be prepared to accept the consequences of sleeping with the husband of a divorce lawyer 
Once I'd done that, I felt sooooooooooooooo much better. I also drove up to her house (2 hour trip) at 1am once and sat outside. Just knowing that I could have turned her life upside down (by telling her husband) made me feel better. I could have done all sorts of things but I sat there for 10 minutes and then drove home. I am a better person than she will ever be.
I just hope my email put the fear of christ in her and stops her sleeping with someone else's husband and boasting and joking about it.
My only regret is not issuing that petition. I had it all drafted, cheque written ready to issue then kids got CP and by the time I was able to go to court I'd run out of time (6 month rule about being aware of adultery) so am re-drafting to issue on behaviour.