PaperCraft

You can make the neatest things out of paper.  These are 3D models.

Paper Kunai - design txt instructions

Naruto Leaf Village Entrance Model - Example  Page 1  Page 2

The Sasuke Barrel Toy - I made this one myself.

Barrel Page 1   Barrel Page 2   Instructions

Frog - Need a summon for your Naruto cosplay?  Pattern- orange frog   Instructions

Welsh Corgi - Great prop for Cowboy Bebop cosplayers.  Ein-orange   Normal Black Corgi(PDF)  Instructions(PDF)

Links to more designs.

Funny Character Cafe - Yes, with a name like that it can only be a japanese site. They have a DIY doll for the Prince in Katamari!

Yamaha Japan - They started making their bikes as paper models and now they have animals, and seasonal things too. Really great selection, and great stuff for Japanese holidays.

Cannon Japan HP in English - Animals, buildings, seasonal stuff and costumes. They seem to have added quite a bit more stuff recently.

CHAO Labratory - Some pretty crazy stuff.  Very geometrical designs.