I just installed Galileo and I went straight to the update site to install Google App Engine plugin but for some reason after adding the site (
http://dl.google.com/eclipse/plugin/3.5) and following the instructions, Galileo simply didn't do ANYTHING after I clicked on the "Next" button, anyway I found the zip files here and it is just as simple as any other plugin.
Download the zip file here for you version.
Unzip it at the "
dropins" folder in your Eclipse (Galileo) directory.
That's it ;)