In terms of appropriateness to a beginner class, the top three websites chosen by my 2009-2010 TDJ3M students were:

• Creating 3D Text on a Cylinder in Google SketchUp
  http://www.sketchucation.com/creating-3d-text-on-a-cylinder-in-google-sketchup/
• Creating a Twisted Bar in Google SketchUp
  http://www.sketchucation.com/creating-a-twisted-bar-in-google-sketchup/
• Google SketchUp Tutorial 2 (Build a House)
  http://www.kongregate.com/games/briancopeland/google-sketchup-tutorial-2-build-a-house
  

Other Resources:

• Gary M. Katz Online "Charts & Drawings" - many excellent resources for SketchUp, including downloadable components and videos. Be sure to check out the bookcase video (WMV file). 
  http://www.garymkatz.com/charts_drawings.html
• Google 3D Warehouse
  http://sketchup.google.com/3dwarehouse/
• Google Building Maker
  http://sketchup.google.com/3dwh/buildingmaker.html
  
• Google Model Your Town Competition
  http://sketchup.google.com/competitions/modelyourtown/index.html
• Google SketchUp 7 for Dummies (videos)
  http://www.aidanchopra.com/tableofcontents
• Google SketchUp Blog
  http://sketchupdate.blogspot.com/ 
• Google SketchUp Video Tutorials (from Google)
  http://sketchup.google.com/training/videos.html
• SketchUp on Twitter
  http://twitter.com/SketchUp
• SketchUp 1: The Basics
  http://www.detaildesignonline.com/software/1366
• SketchUp2India Tutorial
  http://www.sketchup2india.com/tutorial/toc.html
• 3D Landscape Design & Google Sketchup -- from the website: "I use a program called Sketchup for my 3D garden design. There is a free version and one that you must pay for, which has a few more features. However, most of the time I create landscape plans in plan view first. Plan view is a 2D design, where you view it as if you were above the property and looking down on everything."
  This isn't really an educational resource; it's just a great site to see how SketchUp is being used by a professional landscape artist.
  http://www.landscape-design-advice.com/3D-landscape-design.html
• Popular Woodworking Magazine and Woodworking Magazine projects
  http://sketchup.google.com/3dwarehouse/cldetails?mid=77e428242b7b0e876cb99ff1a702c4e9&prevstart=0&start=0