Your iPhone is a great place to store receipts and there are lots of apps in the App Store that offer this feature. Whether you need to keep track of business expenses to turn in to your employer, want to keep track of receipts as a self employed individual, or just want to know where your money is going, OneReceipt is a great option.
Not only can OneReceipt import receipts in many different ways, but let you categorize them in ways that makes it easiest for you to manage them.
OneReceipt is an iPhone app that gives you a very organized way of keeping track of and saving receipts. It will automatically grab emailed receipts (from, say, Amazon or iTunes) from your Gmail account and add them to your OneReciept account or you can take a photo of a physical receipt.