Reliable sources for photographic stuff:

Archival Methods
Supplies for archival mounting and display; similar to Light Impressions, but much more reliable.

B&H Photo
General photographic supplies

Freestyle Photographic Supplies
General photographic supplies; education oriented. They are committed to traditional photography.

KEH
Good source of used equipment

Photo-Eye Books
Photography books; store in Santa Fe, NM

Photographers’ Formulary
Photo chemicals, supplies for alternative processes