When you enter in a cash transaction, you can opt to have the site count that amount as part of the most recent ATM withdrawal that the site learned about via integration with your bank's online banking system. That way you can recall at the end of the week or month what you're spending your withdrawn cash on. Most online banking systems don't offer any way to track that.
Manual entry also works for pending transactions like checks. You can type in the check number and payee so when the check actually clears on your bank's servers, Mint.com will recognize that as the transaction you'd previously entered. This feature lets you track your balance more accurately — especially useful when you're close to the bottom of that checking account's barrel and you're trying to avoid overdraft fees.
The selling point from Mint is its ability to sync up with outside sources like the aforementioned bank account to help you manage all your finances online in one place without getting buried in paper records. The site was recently purchased by Intuit, which also manages the popular personal finance apps Quicken and TurboTax.
