Why can't my computer automatically show me things that will help me with what I'm doing, instead of making me search around for them?
The goal of the dashboard is to automatically show a user useful files and other objects as he goes about his day. While you read email, browse the web, write a document, or talk to your friends on IM, the dashboard does its best to proactively find objects that are relevant to your current activity, and to display them in a friendly way, saving you from digging around through your stuff like a disorganized filing clerk.
For example, if a friend IMs you and says "I can't wait for our camping trip this weekend!" the dashboard will show things like your recent emails about the camping trip, your camping bookmarks, and any files or notes you've got on your hard drive about camping.
Dashboard is being developed in the GNOME CVS repository.
We have a mailing list for core developers.Dashboard bugs are tracked on bugzilla.gnome.org. We also maintain an autogenerated list of FIXMEs from the code, which can be a nice place for new contributors to start.
There is technical documentation, which is worth reading.
If you want to extract the images from the presentation, just unzip the SXI file as you would any .zip file.