How to get Java 6 in OS X 10.8 (Mountain Lion)?
The simplest solution I found is to


Download the jdk6 (download button is on top right)
Unpack it to somewhere. Preferably to /System/Library/Frameworks/JavaVM.framework/Versions/1.6. This is what it looks for me:

&gt; ls /System/Library/Frameworks/JavaVM.framework/Versions/1.6                                                                                                    
Classes       Commands      Home          Info.plist    Libraries     MacOS    Resources   version.plist

Set your $JAVA_HOME to your new location by doing export JAVA_HOME=/System/Library/Frameworks/JavaVM.framework/Versions/1.6/Home/ before your $PATH in your ~/.bashrc (or ~/.zschrc) file
Prepend $JAVA_HOME to your $PATH by doing this export PATH=$JAVA_HOME/bin:/usr/bin:/bin:/us..........
Restart your shell or do source ~/.bashrc