Everyone is familiar with the Mozilla Firefox Web browser, and the audience for the OpenOffice.org office suite continues to grow, but those programs are only the tip of the iceberg. Presented here are just a few of the powerful open-source alternatives to major commercial software that can help keep your small business humming on a shoestring budget--provided you can handle a few rough edges.

Stamp Out Viruses

Antimalware software is so essential for today's PCs that it's virtually a usage tax on computing. Thankfully, you have one alternative for which you needn't shell out a dime. ClamWin can spot viruses, Trojan horses, and spyware on any version of Windows, including Vista.

Based on the open-source ClamAV engine, ClamWin offers a detection database that includes almost 200,000 malware signatures and is kept current via automatic Web updates. On the downside, ClamWin has no real-time scanning capability--that is, it won't automatically verify files when you load and save them. Instead, you have to scan files and folders manually, so you'll need to be aware of potential virus risks and behaviors.

ClamWin also requires more manual intervention to remove suspicious files than most commercial antimalware packages do, but its scheduled scanning feature, combined with its helpful integration with the system tray and Explorer's contextual menus, make it a viable option for most power users.

Serious Number-Crunching on a Budget

OpenOffice.org provides the most popular open-source spreadsheet application, but a lesser-known alternative called Gnumeric offers more-advanced features. As of the latest version, it's now available for Windows 2000 and later, in addition to Linux.

Users report that Gnumeric is very fast, especially when handling large spreadsheets--sometimes even faster than Excel. It also offers better overall compatibility with Excel documents than OpenOffice.org does, but some popular Excel features, such as pivot tables, have yet to be implemented. On the plus side, scientists and mathematicians in particular will appreciate Gnumeric's advanced, flexible plotting capabilities.

Perhaps Gnumeric's biggest drawback, however, is that the Windows version is still very new. Downloading and installing it can be an arcane process, and Microsoft Office users might find the user interface less polished and user-friendly; people migrating from Excel will doubtless have to dig around and experiment to figure out how some of its features work. Still, if you're looking for a mature, powerful spreadsheet application that won't put a dent in your wallet, Gnumeric's advantages definitely add up.

Document Creation for the Rest of Us

Adobe's Portable Document Format (PDF) has become the de facto standard for document delivery in a variety of industries. For most folks, PDF authoring means installing lots of expensive and elaborate software. What they don't realize, however, is that PDF is not a proprietary file format. It's a published, open standard--and as a result, open-source software can come to the rescue.

PDFCreator is a lightweight alternative to Adobe Acrobat that makes basic PDF creation as simple as clicking a button. The program acts as an ordinary Windows printer driver, which means it can generate PDF files from any application that can print, and it even supports PDF encryption for secure documents.

What's more, if PDF isn't your bag, it can output to a number of other graphic file formats, including PNG, JPEG, BMP, TIFF, and EPS. Its documentation is a little scanty--the bane of too many open-source projects--but PDFCreator is so easy to use that you'll hardly notice. One caveat: It doesn't work on Vista.

Lean, Lightweight Word Processing

Over the years, word processing software has grown increasingly complex, to the point that Microsoft Word today includes countless features that most people will never use. AbiWord takes a different approach: At just 5MB to download, it aims to make the most out of a small, lean package.

The first thing you'll notice is how much its interface resembles that of older versions of Word--and indeed, AbiWord fully supports the classic Word file format, in addition to HTML, RTF, WordPerfect, OpenDocument, and many others. (Currently, however, Word 2007's .docx format is not supported.)

AbiWord is fast and responsive, and it has all the basic word processing features. Plug-ins provide still more capabilities, including Web-based dictionaries and translation, a grammar checker, and advanced equation editing for the mathematically minded. Murphy's Law suggests that the one feature AbiWord lacks will be the one you need, but whether you run Windows or Mac OS X, you may be surprised at how much such a small program can do.