For small businesses and the newbie entrepreneur I often share open source as an alternative to high-priced, proprietary software such as Norton Antivirus, Microsoft Office, and QuickBooks Accounting. While these are good products, they're expensive and likely to suck the user into an annual cycle of buying new versions at increasingly higher costs.
And those costs increase not only in terms of product purchase price, but in system conflicts, system bloat, learning curves due to functionality changes, sometimes even in forcing the user to buy new equipment altogether just to "keep up."
When it comes to accounting software I recommend any business owner speak with their accountant before using any of the applications available. There are a number of things that should be considered as you evaluate various accounting packages.
Some of the considerations are, how big is the business, what type of business is it, are you, but business owner, doing the bookkeeping or is there a bookkeeper, what software does your accountant support (might make your life easier when it comes to taxes or audits). For a complete discussion about this go to GReat Kreations.
Having said all of that, here are three of the best and most popular open source accounting packages available:
OSAS Open Source Accounting Suite - OSAS is award-winning accounting software for Windows, Linux, UNIX and Mac users. OSAS can be used by churches, charities, and small corporations. The main features of this product include separation of duties, General Ledger Accounting, Cost Center Accounting, Budgeting, Donation Accounting and Reporting.
GnuCash Financial Accounting Software - GnuCash is personal and small-business financial-accounting software, freely licensed under the GNU GPL and available for GNU/Linux, BSD, Solaris, Mac OS X and Microsoft Windows. Designed to be easy to use, yet powerful and flexible, GnuCash allows you to track bank accounts, stocks, income and expenses. As quick and intuitive to use as a checkbook register, it is based on professional accounting principles to ensure balanced books and accurate reports.
Grisbi Personal Accounting - Grisbi is a personal accounting application running under GNU/Linux and Windows, released under the GPL licence. Grisbi can manage multiple accounts, currencies and users. It manages third party, expenditure and receipt categories, as well as budgetary lines, financial years, and other informations that makes it quite adapted for associations (except those that require double entry accounting).