Using a website called Mint now. You start by adding all your accounts and credit cards. Then you see an overview of all your spendings in nifty colorful graphics. I was shocked at what I was spending on lunches and dinners and have since then cut back drastically.
You can set up limits for each category (gas, food, shopping…). If you overspend, Mint will send you a warning.
Not yet saving money BUT paid of one credit card, last year’s taxes and am going on a vacation. So it does seem to pay off.