PowerPCDownloads
Since 7.04 Ubuntu, PowerPC downloads of Ubuntu are not available on all Ubuntu mirrors. They have been moved into the ports section of the main mirror.
Daily build of the current Ubuntu development release
At present, the current Ubuntu development release is 12.04 Precise Pangolin.
The standard PPC CD image is above 700 MB when fully downloaded and cannot be burned onto a CD.
11.04 and 11.10
For 11.04 and 11.10 use the minimal CDs and follow instructions in this post.
10.10 Maverick Meerkat
The standard PPC CD image is above 700 MB when fully downloaded and cannot be burned onto a CD.
10.04 Lucid Lynx LTS
Ubuntu
Desktop live install CD, server install CD, server install image, alternate install CD, and netbook live install image for various platforms
Kubuntu, Xubuntu, etc
Xubuntu http://cdimage.ubuntu.com/xubuntu/ports/releases/lucid/release/
Kubuntu http://cdimage.ubuntu.com/kubuntu/ports/releases/lucid/release/
It is always possible to install by using the server CD and then installing either the kubuntu-desktop, edubuntu-desktop, or xubuntu-desktop packages via apt-get or aptitude.
8.04 Hardy Heron
Desktop (Live cd), Alternate (text mode installer), and server cd.
Kubuntu, Edubuntu, Xubuntu
Kubuntu http://cdimage.ubuntu.com/kubuntu/ports/releases/hardy/release/
Edubuntu http://cdimage.ubuntu.com/edubuntu/ports/releases/hardy/release/