I'm trying to set up my brother (who has a PPC Mac, with 1 ghz processor and 256 ram) with a Linux distro that would allow him to surf the web on the device. Support has faded for the new browsers, rendering the device essentially useless when it comes to the web. Ideally I would have installed jolicloud, but alas, it is only Intel Mac compatible. Which distros still continue support for PowerPC?
I run Ubuntu 10.4 on an old 1.3 GHz PowerPC G4 iBook with 1 gig of RAM as a secondary laptop to mess around with. It runs OK with GNOME. You're going to be hurting with only 256 megs of RAM so if there's any way to upgrade, I'd suggest getting more RAM.
PenguinPPC has a list of distros with PowerPC support. Ubuntu and Debian are the ones I've used. Arch Linux and Gentoo support PowerPC but are compiled from source which you'll probably want to stay away from on an older machine like yours. Yellowdog is another one to consider, it is exclusively for PowerPC.
I personally like Ubuntu since its a desktop oriented distro, has stable release points (I run the LTS version), and offers a variety of desktop environments which is useful for older machines like yours.
For 256MB of RAM you have to look at lightweight distros, or use a minimum install and build up as you need. The PowerPC requirement may make it harder to find ready-made solutions, but if you are fine with a little work there are many options.
Remember, Linux is all about choice so there are more distros that can be suitable for you. I'm recommending these two because I'm more familiar with them.