Getting even isn't the way to go. It just lowers you to their level. If your spouse is a habitual cheater, then maybe you need to get out of that marriage and find someone who would be faithful to you. If this is the first time, and you can work through this with them, and maybe save your marriage, then that might be the right thing to do. If you feel confident that they wont ever cheat on you again, and you honestly love each other, then by all means work to save the marriage.
The best way to get even is not to get even at all. You have been put through enough pain as it is, revenge is painful and exhausting and can only make things worse especially if you still love the person. Being married is a hard process of loving the same man or woman for the rest or ones life. Depending on how long you have been married sometimes working it out with your spouse is the best thing you can do. On the other hand, if this is something that has happened more than once 9 times out of 10 it will never change and you need to divorce that person and move on with your life and began the process of healing because you can't heal if you keep getting stabbed in the same wound.
The best way to get even is to leave them, and succeed in everything you do. And never look back. Let them see how much happier you are without them, because they are nothing but scum if they cheat on you.
The best way to get even is to make the person pay you for your pain and suffering, i.e. Spousal support or part of their pension. Believe me a dent in their pockets would really hurt.
What is this kindergarten...why get even?. Divorce the idiot or live with it and get over yourself.