There are three items that can be found in pretty much every man's pockets (and every women's handbag) - Keys, wallet and a mobile phone. Given the proximity of your phone to your wallet then, it makes sense that instead of collecting receipts like they were Pokemon, the best way to track expenses is through a smartphone app. We like Expenditure.
Elegantly designed, Expenditure offers a simple way to track your spending on the iPhone. Using the big green button at the bottom of the screen, you simply add expenses as they come up, entering a dollar value, and then categorising your purchase. There's the option to take a photo - which you can use to photograph receipts - and you can set up regular expenses like your morning coffee to automatically add themselves.
If there was one flaw in the app, it's the lack of support to add sub categories. You can create new categories easily, but adding a subcategory of coffee in the food option would offer a little more flexibility to accurately chart your expenses.
In addition to watching what you spend, the app also lets you monitor your income, which helps with the whole budgeting thing. You can also export your data and send it via email in CSV format.
The app costs $2.49, but if it helps you stay on budget, then it's worth every cent. And you can add it as an expense once you download it! Meta...