I was pleased to see that Force.com IDE plugin for Eclipse 3.6(Helios) is now available. You can find the download/installation instructions here. Though there is nothing different to the installation process, you just need to add the same Eclipse-Galileo update site to Eclipse-Helios.
I am happy about this release, as I no more need to maintain two versions of Eclipse i.e.
Eclipse 3.5 (Galileo) for Force.com projects.
Eclipse 3.6 (Helios) for J2EE projects.
Great job force.com tools team. I know its hard to match and release with latest Eclipse versions.