Mint, a web site that lets you see your financial activity from across your bank accounts, has raised $12.1 million from Benchmark Capital and existing investors.

There are a host of competitors with solid offerings of their own, including Wesabe, Geezeo, Cashview and Buxfer. Mint claims it is five times larger than any of them.

Meanwhile, old-school competitors like Intuit have their own online personal finance management sites up in running — check out the online version of Quicken. Mint differentiates itself through patent-pending technology for such things as organizing transactions from multiple bank account, and a better user interface, founder and chief executive Aaron Patzer tells me.

The San Francisco company currently lets you aggregate your financial information from more than 1500 financial institutions. The average Mint user logs in twice a week, and also gets a weekly summary email of their financial activity, and a Mint survey of users shows that more than half have changed their behavior because of learning about their own behavior through the site, Patzer says — people are making smarter financial choices, such as eating out less and dining in more.

The company isn’t disclosing revenues, but it offers a part of its site that features competing credit card financing offers, for example, to help users save money. Patzer says that up to 15 percent of users click through on these ads.

Patzer also says that the company has a number of major announcements in the works, as well, including a big partnership and new features for viewing your investments, mortgages and loans from other financial sites.

Previous investors include Shasta Ventures, Sherpalo, Felicis Ventures, Hite Capital and First Round Capital. Mint raised $4.7 million last fall.