If you are determined to run up his credit, however, your legal liability depends on whether your name is on the account and the laws of your state.
If you do not live in a community property state (Arizona, California, Idaho, Louisiana, Nevada, New Mexico, Texas, Washington or Wisconsin) and you are not a joint account holder, you are generally not legally responsible for your husband's credit account balances. This is true even if you are anauthorized user. (If you're not an authorized user, using his cards could get you in more trouble. Don't do it.)
If you're in a community property state, consult with a legal professional where you live. In some states, the marriage ends for community debt purposes when you no longer live together, whether or not you occasionally see each other. In other community property states, you can be liable for debts that are run up until the divorce is finalized.
Of course, if you are a joint account holder on those cards, it's your debt as much as his. Running up joint debt is like shooting holes in a boat you're both sitting in -- it's dramatic, but you might regret it after you've made your point.
Let's look into the future. You and your husband have two choices: patch things up or get a divorce. What happens to the debt in either case?
Say he turns around and is sorry, you forgive him and the two of you recommit to your marriage. Imagine you're back to smiling over the breakfast table and all is well -- and then the bill comes with the credit card damage you did when you were angry. Now you've got something to fight about, and you have to help pay every penny of it off, plus interest. Uh-oh.
On the other hand, say you decide he is incorrigible and you want to move on. You file for divorce. Those credit cards bills with a sudden spate of purchases at pricey clothing stores and spas will haunt you in divorce court. You get less in your settlement because of those debts. You lose again.
I don't blame you for being angry. Coming home from Iraq to a cheating husband seems like more trouble than a person should have to bear. I hope your marriage is salvageable, but if it is not, the best revenge is to do well without him. Put down the credit cards, and instead start setting boundaries with your husband.
Take care of yourself and your credit!