Mint.com is a free online personal finance and budgeting service that aggregates all of your banking, credit card, loan, investment and property information, helps you create a budget, and automatically assigns each expenditure to a particular budget line.
Track your spending and keep to your budget with Mint. Click to view larger image.
The Mint Android app gives you an easy-to-use and surprisingly thorough view into your Mint.com account, with a summary of your current total account balance, where you stand on your budget, and a rough monthly cash-flow analysis on the home screen.
Alerts also appear on the home screen, letting you know things such as when an account balance is low, when you're over budget in a particular area, or when you've received a large deposit or bank fee. Drilling down lets you view every transaction on each bank account or credit card, and assign it to a budget line if Mint.com hasn't already done so automatically (which it's surprisingly good at).
Make sure you set a four-digit passcode in the settings -- although you can't make withdrawals or transfers through Mint.com, you probably don't want your entire financial history to be available to anyone who happens to pick up your phone.