I have purchased the new Adobe Illustrator CS4 and starting working with its vector features. I vectorized the trees on this websites header, but I want to know how to do more in depth graphics and vectors using this program. I have nearly masted photoshop, if anybody could direct me to any quality tutorials or pieces of information on this subject, it would be greatly appreciated.

http://vector.tutsplus.com/
http://www.ndesign-studio.com/resources/tutorials/

Tutorials won't be of any use to you. They can teach you tricks, and tips, but the skill needed has to be mastered by you only.