I found a wonderful source at Wool Obsession for anyone trying to understand the various types of fibers available to spin and what they look like.  You can compare flax to hemp,  cashmere to mohair, and much more. The blog also lists current ebay auctions for the type of fiber shown.

As a new spinner, I am not only trying to learn about fiber types, but also the many different sheep breeds and their various wool characteristics.  I thought Rambouillet was a poet? What do Targhee wool and Merino wool have in common?  Good site for quick info and good auctions! (Hey, they even list Yak fiber!)