Paper Museum has colorful, detailed Japanese paper diorama sets. Scenes include outdoor market, stores, cafe, rooms in a house.
Sasatoku is a Japanese site with cheerfully bright model sheet downloads for objects, dolls, vehicles, animals, cards, and paper automata.
Handmade Papercraft Club is a Japanese site with beautiful, uncolored intricate designs. Downloads for pop-ups and mobiles.
A variety of cute, colorful paper toys. Boxes, models, moving toys, puzzles, cards.
Paper Crafts at Yamaha Motor
Realistic models of motorcycles, animals of the world, rare animals, animals from Japan, and seasonal paper crafts. Dioramas, mask, buildings...
Two other excellent resource blogs for papercraft models are Paper Forest, Papercraft Paradise, Papercraft World
ETA 2/24/08: Another page I found through Darthverso on my del.ici.ous network is a review of some of the the best papercraft toys. My eyes were popping out of my head. 100 Free Paper Models and Toys