Many of the free desktop publishing software programs are really specialty utilities. They are fine for a specific job — such as labels or business cards — but they aren't your all-around page design tools. However, there are a few free programs with full desktop publishing capabilities.
If you're looking for PC software, see free desktop publishing for Windows.
This Open Source desktop publishing software is available for several platforms, including Mac. Scribus offers CMYK support, font embedding and sub-setting, PDF creation, EPS import/export, basic drawing tools, and other professional level features. It works in a fashion similar to Adobe InDesign and QuarkXPress with text frames, floating palettes, and pull-down menus — and without the hefty price tag. Probably the premiere free desktop publishing software application. It has the features of the pro packages, but it's free. However, Scribus may not be the best choice if you don't have the time or interest to devote to overcoming the learning curve associated with high-end professional level software.
Scribus 1.4+ for Mac and Linux, Windows
Not just as good as, some say it's better than Microsoft Office. Get fully-integrated word processing, spreadsheet, presentation, drawing, and database tools in this Open Source software. Among the many features you'll find PDF and SWF (Flash) export, increased Microsoft Office format support, and multiple languages. If your desktop publishing needs are basic but you also want a full suite of office tools, try Apache OpenOffice. However, for more complex desktop publishing tasks you might be better off with Scribus or one of the print creativity titles for the Mac.
Apache OpenOffice 3.4+ for Mac and Windows, Solaris, Linux
A popular free, open source vector drawing program, Inkscape uses the Scalable Vector Graphics (SVG) file format. Use Inkscape for creating text and graphics compositions including business cards, book covers, fliers, and ads. Inkscape is similar in capabilities to Adobe Illustrator and CorelDRAW. Inkscape is also being used to create fonts. Although it is a graphic software program it's quite capable of handling some page layout tasks.
Available as of 2011: Inkscape 0.48 for Linux, Windows, Mac, and will run on FreeBSD, Unix-like systems
Also see: More Vector Illustration Software for Mac