I was looking through the 250+ new features and improvements for Lion (available for $29.99 as an upgrade in July) and found this little gem in the Safari Improvements:
Improved graphics performance
Web pages that use the HTML5 Canvas element can tap into the graphics processing unit on your Mac to display graphics and animations. With improved hardware acceleration for Canvas, games and interactive web applications render faster and smoother in the browser.
Another little gem I found is something that we have needed for long time.
Capture a region of the screen
QuickTime Player lets you record part of the screen, such as a specific window. It’s perfect for creating a video tutorial of an application.