This may be old news for you but here goes:
http://web.archive.org/web/*/http://3dfx.com
Some pages marked with "*" work :D
Like this one:
http://web.archive.org/web/20000510022247/http://www.3dfx.com/
And the original 3dfx Forums:
http://web.archive.org/web/*/http://3dfxgamers.com
The server sometimes loads slowly, you may need to use OpenDNS from http://opendns.com/
Bye :D
cool, i'll have a nice look!