For a real good time, call r/GRATEFULDEAD!

Official Sites:

Grateful Dead
Furthur
Bob Weir and RatDog
Bob Weir's Website
Mickey Hart Band
Rhythm Devils
Tamalpais Research Institute
7 Walkers
BrentMydland.net
Hunter Archive
Grateful Dead Archive at UCSC
GD Ticket Service — Ticket Order Office

Looking for Grateful Dead Tapes?

Internet Archive -- Tips and Best Practices
Mediafire 1 2
Top 100 SBD’s

Sail Through the Torrents:

Intro to Torrenting for Deadheads
etree
gdvault
Lossless Legs

Related Reddits:

r/phish
r/musiccritics
r/jambands
r/trees
r/psychonaut
r/widespreadpanic
r/stringcheeseincident

Very Cool Stuff:

Map of r/GRATEFULDEAD Hedditors — Click on your location, add your name, maybe some information or a favorite lyric.
Heady Version — like a reddit for live Dead songs!
Dead Podcast
The Annotated Grateful Dead Lyrics
Rukind Grateful Dead Tabs
Darks' Grateful Dead Tabs
GDRadio.net — streaming Grateful Dead, Ratdog, Jerry Garcia Band, Phil and Friends, Furthur (and more) 24/7!
nugs.net — Almost too much live jams. Stream the Dead and all their distant relations, and download all of the music! ListenToTheDead.com
The Grateful Dead Hour with David Gans