Prequel Watch has a great article on the impending lightsaber duel between Anakin/Vader and Obi-Wan. Currently, there are a few production pieces that are being worked on:

• Hayden Christensen has already begun a rigorous work-out regiment. As they put it, he's "beefing up" and getting into top physical shape. In a recent issue of Star Wars Insider Rick McCallum stated that "Hayden will change physically in this film." He's going to be bigger... and not just for the Vader stuff. It also means Hayden as Anakin will likely be a more imposing figure as well. Hayden starting lifting weights and working out 6 weeks ago... and he will continue to keep in shape all the way into and through the end of filming (another year or two).
  
• Nick Gillard is already blocking "at least one" duel between Anakin/Vader and Obi-Wan. In fact, he began some work in August.
  
• Both Hayden and Ewan McGregor will report to Fox Studios Australia as soon as late February or early March to begin working on the duel(s)...a full 3-4 months before shooting begins. (Principal Photography is still set to kick off on June 26, 2003).

Cool stuff! Be sure to go here to read the full article! I am eagerly anticipating what Episode III has in store for us. It is also hard knowing that it will all end as well. After living with Star Wars since its inception in 1977, it has become a way of life for me. What will become all of the fan sites? Only time will tell.