Using just a piece of paper, you can create the Gmail logo origami! Origami by Gilad Aharoni.
Gmail Origami via P&P

This is a paper craft model of a Japanese style top, a popular toy played with by Japanese children since times of old. Play with this Origami Spinning Top by placing it on the floor or a desk, and blowing on it from above. Try blowing harder or more softly and use tops of different shapes, colors and patterns to see how they change-Canon

Spinning Top Origami

This is one amazing work of art!!! It took one year to design this masterpiece which was based on Parthenon of Athens. It has 58 complete columns when opened and uses a unique designed interlocking system. This one is not for free though. You can download it for $39.99 US dollars.
Athens' Parthenon Origami Pop Up Card

Here's another project from the guys at foldplay.com. I haven't printed it yet but I'm sure this nerdcatcher origami game is a fun one.

Nerdcatcher Origami

Theres a couple of new models at the HP site. Get these colorful 3D Chinese zodiac animals together with trains, animals, an insect, a robot and even some origamis. Choose "toys, stickers & puzzles" for the category and then "games" for the subcategory to find the other 3D models.
HP Paper Models

Download that simple pig model along with a couple of papercrafts(mansei special, samurai on a fish and more) and origami models. A simple Christmas tree is also included.
niku-mansei