Accounting Systems on Linux?

cuebei asks: "OK, Slashdotters - let's talk accounting systems for small-mid sized businesses. With the popularity of Linux servers running various e-business services such as web, directory, mail, commerce, etc, it only makes sense for Linux to become a more mainstream platform in the business world. One of the areas where I can foresee Linux being used extensively is in the area of accounting. Linux is both reliable and scalable, two key requirements for any accounting package. So who uses Linux for HR/Accounting? What options are out there? Open-source or commercial? If you were starting your own business and standardized on Linux as a platform, what accounting package would you use and why?"