The latest release of the EnergyPlus building energy simulation program, Version 3.0, was completed on November 13, 2008 and is now available in versions for both the Windows and Linux operating systems. (Macintosh version will be available within a few days.)

EnergyPlus V 3.0 is available at no cost from the EnergyPlus web site:

Energy Design Plugin for Google SketchUp:
The Energy Design Plugin is a free plugin for the GoogleSketchUp 3D drawing program. The plugin makes it easy to create and edit the building geometry in your EnergyPlus input files.

EnergyPlus Example File Generator: A Web-based service is available that creates and runs EnergyPlus input files for simple models of commercial buildings. This is a pilot project and is currently made available only as a BETA service. You can access the service and customize the characteristics of the building you want to model on the EnergyPlus Example File Generator Application (pop-ups must be enabled).