Recommended: The Paper Mill Store & Green Field Paper Company

If you're looking for quality paper in bulk for you DIY projects, try the Paper Mill Store, which offers a wider range of colors, weights, and sizes all in one place than I've seen elsewhere, including acid-free/archival/ph neutral options, recycled stocks, and even a few papers made using windpower.

They also have a bunch of free templates available for download here.

If you want to go completely treeless (& have a little more $ to spend), take a look at Green Field Paper Company, for writing, cover, and drawing papers made with hemp fiber and recycled papers with up to 75% pcw content. They've also got a line of decorative handmade papers, made with garlic, coffee chaff, and even 100% recycled junk mail.

Neato.

UPDATE: Scott Pierce points to Vision Paper for tree-free options as well. (Thanks, Scott.) I've written for sample swatches and a price list. Their papers are made from kenaf, a member of the hibiscus family.

ANOTHER UPDATE: I received my order from the Paper Mill Store . . . along with a sample mini pack of some beautiful glossy Kromekote by Smart Papers as a free sample. They rock.