The Permanence and Care of Color Photographs: Traditional and Digital Color Prints, Color Negatives, Slides and Motion Pictures, by Henry Wilhelm and Carol Brower. A PDF version of the complete book, published in 1993, is available free at http://www.wilhelm-research.com/book_toc.html. This epic book (744 pages) is the result of 20 years of research into the aging characteristics of specific photographic materials, and shows that some color film and print materials last much longer than others.
Wilhelm Imaging Research does long-term permanence testing of printer inks and photo papers and publishes the results on its Web site http://www.wilhelm-research.com. If you want to know how long your digital prints will last, look up your printer here.
The Northeast Document Conservation Center (http://www.nedcc.org) specializes in the preservation of paper-based materials. It provides a wide range of resources and services, including a free online course in document preservation.
FACTS (Fine Art Care and Treatment Standards) is a nonprofit organization dedicated to "improving the care of art and keepsakes through education, research and consensus standards". A wide range of informational and instructional materials are available (see http://www.artfacts.org).
The Library of Congress provides information on the care, handling and storage of valuable collections, including a guide to oreservation matting and framing and emergency procedures for dealing with water damage (see http://www.loc.gov/preserv/careothr.html).