Textures to The Max - high end 3d Materials libraries from the real world
Great site for 3dsmax textures but the download section for free samples does not work.
Bad link.

Textures Volume 1 Samples
This redirects you to a list of sponsored sites for shopping.
Bad link.

everyday...
This redirects you to a list of sponsored sites for shopping.
Bad link.

Megalodon Teeth Catalog
A big collection of shark teeth - Photos in jpg format (strange link, but it works).

The 3D Studio - Textures
Page not found.
The correct link for this site now is http://www.the3dstudio.com/product.aspx?id_category_0=2
Commertial site - Only few textures free to download.

NOCTUA Graphics Website
Herbert Fahrnholz Textures Free to download - Several categories - Good collection in jpg, most of them seamless, no bump maps (512 x 512 pixels).