These are a bit old. Links sent to/from Leah.

Online:
Transmaterial is a catalog of materials, products and processes that are "redefining our physical environment." The whole thing is available as a free 187 page PDF. Makes you wish you had a laserjet printer. Material types include multidimensional, repurposed, recombinant, and intelligent. Among them is Superblack, the blackest black in the world (also seen at Cabinet Magazine's Chromophlia event).

Offline:
Materials Monthly is a subscription-based publication that sends you innovative material samples and fetishy product sheets with graphics, material descriptions, technical/performance specifications, manufacturing processes, etc. It's $179 for ten issues, but you can get a free sample of Reversacol, a plastic that changes color when exposed to light, by filling out a form on their website.

Free goodie: geocoder.us will give you the latitude/longitude for any location in the US.

Also-

Nice retro-future images up at City of Tomorrow. Too bad about those porn banners at the bottom. (via overmorgen.com) Similar sources for sample repository up at Tick Tock Toys