Where can I find the Linux distribution for the ppc architecture?
I guess the best distro for the PowerPC based PC is Yellow Dog Linux (YDL). Just like other distro it is a free software and open-source Linux distribution for Power Architecture hardware. It is based on Fedora Linux. According to wikipedia:
PowerPC is a RISC microprocessor architecture created by the 1991 Apple–IBM–Motorola alliance, known as AIM. Originally intended for personal computers, PowerPC CPUs have since become popular embedded and high-performance processors as well. PowerPC was the cornerstone of AIM's PReP and Common Hardware Reference Platform initiatives in the 1990s, but the architecture found the most success in the personal computer market in Apple's Macintosh lines from 1994 to 2006 (before Apple's transition to Intel).
PowerPC based system includes Sony PlayStation PS3, IBM Power and pSeries, Mercury Cell, Apple Macintosh G3, G4 & G5 computers, including iBooks, PowerBooks and Apple PowerPC etc.
Download PowerPC Linux distributions
Please note that you can also try out FreeBSD, OpenBSD and NetBSD for the PPC architecture based system.