Planetarian
Fan site and English patch for the visual novel "Planetarian" by Key.
http://planetarian.insani.org/

Hæleþes gemot
Popular English forum for visual novel discussion.
http://forums.haeleth.net/

Narcissu
Official website for the English version of the homemade visual novel Narcissu.
http://narcissu.insani.org/

Ren'Py
An interpreter for creating and playing visual novels, written in Python.
http://www.bishoujo.us/renpy/

al|together
An annual event for translating amateur visual novels into English. Includes free downloads for all completed games.
http://altogether.insani.org/

LadyStar
Online American visual novel written in Flash. Seven girls find magical treasures that give them the power to transform into Ajan Warriors.
http://www.ladystar.net/

Zapdramatic
Flash games in the visual novel format, oriented around improving your negotiation skills.
http://www.zapdramatic.com/

Digital Novel Markup Language
"DNML" is a markup language for creating visual novels.
http://www.geocities.com/yunaffx2001/dnmln.htm