I've only been using these site for 2 days now, but I've completely fallen in love with it. It's Mint.com! All you do is link your accounts, such as savings, checking, etc. and it puts together a monthly budget for you or you can enter in your own budget perameters. Mint will create pie charts and bar graphs to illustrate how and where you spend your money.
But don't just take my word for it, here are some videos to let you get a look for yourself.