As far as many people are concerned, GNU Emacs is the real Emacs. I've used a version of Emacs since 1984, and until very recently it was my editor of choice for all editing tasks. It is still my editor of choice for many editing tasks.

General Info

GNU Emacs FAQ
The FAQ
Emacs Lisp Archive
A searchable interface to the Ohio State elisp archive. Unfortunately, the Ohio State archive is no longer well maintained.
GNU Emacs for Windows NT and Windows 95
Emacs for NT - A heroic effort to make Emacs run on Win32 operating systems. Recommended.

GNUS

Gnus is the most flexible, customizable newsreader I've ever used. It's my newsreader of choice, but it's pretty slow, and it's single threaded (thank you Emacs). If these two issues could be addressed, I'd be happy as a clam.

Gnus Newsreader Homepage

BBDB

bbdb is a cool package which hooks up to GNUS or another Emacs mail/news agent and maintains your address book. This sounds blase now, but BBDB has been around for at least 10 years.
 
The Insidious Big Brother Database
Keep track of everyone - JWZ's version of the page -- after all, he invented it.
BBDB addons
Among the most useful addons are bbdb-query.el bbdb.pl and bbdb-show-all-recipients
The Insidious Big Brother Database 2.X
The active development trunk for BBDB

Miscellaneous Modes

html-helper-mode HTML helper mode beta
HTML editing Mode
Emacs font/face files
html fontification
Directory of /pub/st/stig/src
stig paren
David's Elisp hacks
tempo.el
Mic's Emacs Hacks
mic-paren, shell-toggle
Index of /~mic/ftp/emacs/
ffap
Anders Lindgren's Emacs page
Follow Mode, Folding Mode
AUC TeX - Table of Contents
AucTeX editing Mode
The Emacs World Wide Web Browser
W3 Emacs Browser
browse-url
Send a url to the web browser
PSGML: A GNU Emacs mode for SGML files
XML/SGML Editing mode
Ebenezer's software for TEI
How to setup PSGML
Emacs code by Stephen Eglen
iswitchb
public_emacs
WoMan
Jim Blandy's elisp
dafft, dired-tar
Noah Friedman's elisp
fshell, geek.el, ssh.el, vcard.el
The Custom and Widget Packages
Easy customization
UTA - Jari's Emacs elisp readme, tips and instructions
Great elisp index and Tiny Elisp packages - Jari Aalto
Andy Norman's home page
efs, ange-ftp, gnuserv
A CSS editing mode for Emacs
Edit CSS Files
Peter Gailbraith's elisp hacks
ff-paths, func-doc
emacs
Ilya's cperl-mode, imenu-go, choose-color
Emacs
Heddy Boubaker's mode-compile, command-other-frame
Bob GlickStein's Home
Emacs extensions including ishl
Eric's FSF projects
Eric Ludlam: eieio, speedbar, checkdoc
A GNU Emacs mode for SGML files
PSGML mode for editing XML and SGML
Emacs
Manuel Serrano's flyspell.el
feedmail
cool smtp mail sender

Java Modes

Jacob - The Java Commando Base
A nice Java and Emacs Class Browser - partially written in Java
Emacs JDE Home Page
Emacs mode for Java - based on cc-mode

Tools/Helpers

These helpers are particularly useful if you are running on Windows
GNU ISPELL V4.0 - Table of Contents
The gnuserv home page
Gnuserv for GNU Emacs for Windows NT and 95
jtelnet - Telnet via NT-Emacs
InterBits (Ted's home page) - shellex.el, w32-help.el
PrintFile. Easy file printing in Windows