Quick-- do you know how much you spent last month on groceries? How about gas? Clothes? Kid supplies? Gifts?
mint.com (sadly, not all of them fell within budget). Mint is free on-line budgeting tool. And it's good, too.
My husband and I started using Mint in May of 2009, so we're coming up on two years use. Before we started using Mint we would generally spend less or equal to our income. But we had no idea how our expenses broke down or where that money was going. We just knew about how much we spent. Now we can quickly and easily account for every dollar, track our spending over time, see trends in our spending and our net worth. Seeing our spending in pretty pie charts or bar graphs makes something as abstract as "finances" more concrete to me.
To use Mint, you link your credit card/bank/loan information to Mint's secure site and it will automatically pull information for you. It will categorize your purchases, pretty accurately for the most part and help you track your spending. Sometimes the categorizing is a little off and needs a bit of fine-tuning, but that's easy enough to do. You can set budgets (monthly or every set number of months, or just a one-time cost) that roll-over to the next month or start anew each period. Mint also offers goal planning tools. Some of them help you save for retirement, pay off credit card debt, buy a car or take a trip.
I'm sort of an evangelist for Mint, because it makes budgeting easier and fairly painless. Gaining a better understanding of how we spend our money has helped me want to be more responsible with it. In our current time of limited income-- really, does anyone have unlimited income?-- it has been so helpful to see where we can trim back and how we could more wisely use what we've got. It's cliché, but knowledge is power.