Ronen Bekerman's running a "HOVER Challenge" — where participants are designing, modeling and rendering structures that appear to float. It's chock-full of information about all things related to architectural visualization. V-Ray, Maxwell, 3ds Max, Photoshop, Fryrender, SketchUp – it's all there. The format is what interests me most: everyone is posting their progress to a forum where others provide advice and encouragement. Two caveats: You need to be logged in to see images, and only some of the participants are using SketchUp.
The deadline is coming up fast October 20th.