AR Media, a brand of Inglobe Technologies, has released an AR plug-in for Google SketchUp. Google SketchUp is a program that can create, modify and share 3D models. The plug-in allows for use those models in an AR environment.
They have versions (AR-Media Plugin v1.1) for both Windows and Mac. An installation and user guide can be found here. A trial version can be downloaded but it only allows the objects to stay on the screen for 30 seconds. The video shows a brief example of the usage. I can’t get a feel for how friendly or easy it is from the video, but its another tool in the AR toolbox.