There's a lot of cool open source, pro-level production software available for Macs: GIMP, Inkscape, Blender, etc. Some of these have dropped support for PowerPC, but you can download older PowerPC versions that are mature and still useful. Scribus is one such example. It's a layout and publishing application for publishers needing a wee bit more than Microsoft Office, yet finding a pre-compiled installer for a PowerPC version was like being on a scavenger hunt. Even their Sourceforge site seemed to be scrubbed of older versions. After a bit of googling, I finally found one lonely download link at 1-2-3 Printing. Scroll down to the link for "Scribus_22.214.171.124_Mac.zip" and download. This version will run on Tiger and up. I also included this in my Mediafire folder in case the above link disappears.
When you first start Scribus, you get this error:
So to use those features, you need to install Ghostscript available here. After installing, then go into Scribus's preferences in the External Tools section, and under PostScript Interpreter enter /usr/local/bin/gs for name of executable. That's the path to Ghostscript. Then you should be good to go.
To get a newer version of Scribus, I suppose you could install it via Macports or Fink, but if you wanna endure that pain, you might as well go full-on Linux:)