Laura's favorite book, and a great introduction to paper-folding, is
Teach Yourself Origami. This takes you step by step from simple to hard, teaching you important folds along the way, like the mountain fold, inside reverse fold, and ever-popular frog base. We could have used these instructions on how to divide a square into thirds while making a small vase, but everything turned out well.
There are a number of good reference sites on the web for finding folds and patterns. Joseph Wu hosts an excellently designed and comprehensive site with many popular designs, such as my favorite, the
Kawasaki Rose. His links section is more comprehensive than I could hope to be here. Someday I would like to create my own designs, but I have yet to find a good book on the subject. Please let me know if you know of one.