Here's a few things of various topics you may want to check out...
Giant Golden Book of Biology - Illustrations by Charles Harper - a triumph of design and illustration!
Creating the cover of a novel. Irish illustrator PJ Lynch shows a step-by-step of how he goes through the process of creating a book cover.
Bear Tools I and Bear Tools II has Kevin Cornell of Bearskin Rug giving us his tools of illustration - guides on pencils, erasers, and inking implements.
Illustrophile, a blog "for lovers of illustration and commercial art" that started last August. It features mostly artists and designers that are currently working.
By the way - if you enjoyed the illustrations by Charley Harper (above), then check out more of his work here and here.