This June-July in San Antonio, I'll be teaching a NECC workshop on Google Sketchup. I'm really looking forward to that. Each year, however, at our local VSTE (Virginia) state conference, I teach a popular workshop on Photoshop. I was recently asked a question about resizing images for the Web, and thought I'd share my tutorial.
Tutorial 3: Cropping and Resizing for the Web from John Hendron on Vimeo.
The big deal here is when you create thumbnails, you don't simply put a "smaller" version of your photo online. Instead, you should perform a crop and zoom. Since you're cutting out real estate in a smaller thumbnail, you should increase the meaning by cropping-out the distracting content.
Manipulation of digital images is becoming a basic lifeskill that needs to be taught--particularly as we guide students into the world of Web 2.0.