Can anyone give me a good reference to a relatively complete list of Item Special Materials, such as Adamantine, Mithril, etc? Most sources are so spread out and lack vital information that it's difficult to find anything worthwhile.
D&D 3.5 special materials
The most complete list of official special materials published for Dungeons and Dragons 3.5 that I could find is the user terronus's salvaged-from-the-Wizards-of-the-Coast-forums Special Materials Index here, hosted on the Giant in the Playground forums.
Although terronus's Special Materials Index really should be sufficient for most campaigns, keep in mind that even it omits, for example, special materials from the Bazaar of the Bizarre column "Secrets of the Master Smiths" (Dragon Annual #5 38-40), the special material ferroplasm (Psionics Handbook 138), and the special material nepthelium (Sunless Citadel 32), this last so obscure I was unaware of it until finding this thread (also a valuable resource yet less navigable). (So you needn't look it up, metal weapons and armor made from nepthelium cost 100 gp more and appear transparent or gemlike; this has no mechanical effects.)
Pathfinder special materials
The d20PFSRD compiles Pathfinder's ever-growing list of 1st- and 3rd-party special materials here.