But I'm also excited about PBS's educator's resources. One that I have regularly used for teaching Mark Twain is the Mark Twain Interactive Scrapbook.
The clickable links guide students through a ton of great primary sources. It's perfect for a web quest or to help you introduce Mark Twain or Huck Finn via a projector or Smartboard.
PBS has lesson ideas, videos, and fun tools like the Puzzle Builder, Quizmaker, and Digital Storyboard. Go check it out!