Recommended Links:

wizards.com/duelmasters
This is the official Duel Masters website where you can sign up to be a D-Max member. Great strategy articles and a huge message forum community and listings for all the premier Duel Masters tournaments…plus lots of cool stuff.

thedci.com
Look up your ranking or read up on all the official Tournament rules. Tons of information for players participating in sanctioned Duel Masters tournaments.

dmgamer.com
An independant site with card reviews, strategy articles and forums.