If you're interested in the Rails 3 side of things, here is also an hour of your time:

* New Router can route other Rails apps, Sinatra apps, and possibly apps from non-Ruby frameworks (he mentions Django)

* New Javascript agnosticism uses HTML5's data-* attributes

* ERB's html_escape on by default, <%=raw to escape escaping

* Lots non-public-facing stuff being refactored