Eclipse recently started to provide Git mirrors of the cvs repositories.You find the location of the Git repository on the following website Eclipse Git repositories.
If you have the git commad line tools installed (Ubuntu: sudo apt-get git-core) you can use the following command to check these repositories out from the command line:
git clone url
for example to get the JFace snippets use the following command.
git clone git://dev.eclipse.org/org.eclipse.jface/org.eclipse.jface.snippets.git
After that checkout you can import the project into Eclipse via File -> Import -> General -> Existing Project into Workspace.
Via Git we have another nice option to get the Eclipse source code in additon to cvs and svn. 🙂
I believe Git does currently not support Project Set Files (.psf) similar to cvs to get a consistent set of plugins but at least individual plugins can be checked out.