Origami
Origami Diagrams - This site features hundreds, yes hundreds, of origami tutorials and diagrams completely free! Learn how to fold ordinary paper into marvelous sculptors. Try out the dinosaur, it was my favorite! They also accept diagram submissions and ideas. Check out this site if Origami isn't really your thing; it has step by step guides for creating samurai hats and boats out of paper!
Photoshop Folded Paper
Gimp Tutorials has a great guide for creating a folded paper look in the photo editor GIMP; this tutorial can also be used for other programs like Photoshop.
Quilling and Paper Piercing
Quilling.com is a great source for all your quilling needs. They update regularly with new ideas and pattern guides you can use to begin your crafts!
Terryfic Times has a great section on Paper Piercing, including a full gallery you can use for ideas and as a guide for your own projects. Have fun!
Napkin Folding
NapkinFoldingGuide.com has in-depth guides to folding napkins, but their tutorials can also be used to develop your own new ways to fold paper into elegant designs!