You can find my collectd 5.5.0 builds on Launchpad.
They'll keep updated for Ubuntu 12.04 and 14.04. Plugins are enabled as long as dependencies could be fullfilled.
Please note that the Varnish plugin has been compiled against Varnish 4 for both builds. You'll need to add the official Varnish Repo on Ubuntu 12.04 to use the plugin.