There’s a new site called Media Queries that shows examples of sites using responsive design principles.
Targeting HTML5’s Semantic Elements with CSS talks about how the author uses CSS selectors to target various new semantic elements that may exist in numerous places on a single HTML5 page.
Videos about the HTML5 Boilerplate and showing how to use it can be found at Paul Irish’s site. The 15 minute one called Getting Started with HTML5 Boilerplate is the most useful.