Reddit mentions of Animal Origami for the Enthusiast: Step-by-Step Instructions in Over 900 Diagrams/25 Original Models (Dover Origami Papercraft)

Cool, which T-Rex? Satoshi has a nice one My favorite from another creator may be John Montroll's fox which I've folded so many times in high school, that I memorized!

I think for my own, my favorite is the mayfly, I just like how it turned out. That and the shrimp are the two most complex models I can fold from memory. With the other ones, I still need to see the crease pattern!

Awesome! Lots of other people linked great references as well, hope you find something that interests you. I've always been fond of animal origami, it's great fun. I also forgot to mention John Montroll's work there - I find his models much simpler compared to Lang's, but no less fun to fold.

I have designed some of my own! To give a sampling, in increasing order of complexity (with diagrams!),

• here's a truncated tetrahedron,
  
• here's a double equilateral unit which can make things like an octahedron, icosahedron, "spiky ball," and many other deltahedra,
  
• here's a rhombic dodecahedron, and
  
• here's a compound of the cube and octahedron.
  
  My favorite origami book is John Montroll's Animal Origami for the Enthusiast, which starts out with simple, charming models and builds up to complex masterpieces like this lobster. It's one you can go back to for years. (I still have my childhood copy, inscribed "Merry Christmas 1988, Love Mom and Dad.")
  
  Another lovely volume, though not an ideal first book, is one called Origami for the Connoisseur. One of its highlights is an exquisitely beautiful seashell model. Here's someone folding it on YouTube.
  
  If you're curious about modular origami, Tomoko Fuse is a master of the field. This book ("Unit Origami: Multidimensional Transformations") is a hefty omnibus with plenty of lovely designs. Fuse tends toward a bit more surface elaboration and fussy preciseness than I go for these days, but her work is absolutely worth recreating with your own fingertips.
  
  Most of all, I'd encourage you to just try things out and have fun. There's action origami that does stuff (fancier versions of jumping frogs and fortunetellers), there's a big "tessellation" scene, where people fold intricate, two-dimensional patterns, there are flowers and franchises and figures. Any decent bookstore will have a papercraft section with an origami book or two. Libraries should have plenty of volumes available.
  
  Enjoy!

I recommend starting simple and working your way up to more complicated stuff. I got started with this book:[Animal origami](
http://www.amazon.com/Animal-Origami-Enthusiast-Step-Step/dp/0486247929)
It has lots of models, and they get progressively harder, but start really simple.

If you don't want to buy anything just yet, I would suggest at looking though the models here: origami.org and just work your way up form simple to complex