Marianne Walker is the Product Specialist who trains the Certification Instructors for Copic Markers. Her blog is: http://ilikemarkers.blogspot.com/ and if you go down a bit on the right and start in her 2008 archives there is a LOT of valuable tutorials in there!!
There's also some exciting new things coming out at CHA this month including this much anticipated book on Shading! Notice the blog post title says part 2, there are other updates to check out as well ;)