Browser Based

Abiator's Adventure Arcade
Mazes of the pick-a-path style including a The Hobbit game.
http://www.berghuis.co.nz/abiator/pick/mazeframe.html

Altered Reality - Interactive Murder Mysteries.
Interactive murder mystery where you set the direction of the investigation. Examine forensic reports, autopsies, interview transcripts and crime scene photos as the mystery unfolds. Each mystery runs for 2 weeks.
http://alteredreality.com.au/Online/

The Boondocks
Dedicated to the ongoing virtual story of the USS Batfish SSN-736, a chat simulation about a submarine in the US Navy.
http://www.angelfire.com/tx3/theboondocks/

Castle Arcana Gothic Mansion
Take a stroll through the gardens, get lost in the Hedge Maze, explore hundreds of strange rooms, but don't drown in the pond.
http://www.castlearcana.com

Crime Scene Evidence
Help investigators solve crimes in Oxford, Mississippi. Examine the evidence online. Participate in crime scene investigations by asking questions, offering observations and providing leads. Updated weekly since January 1995.
http://www.crimescene.com/

Daelindor - The Dark Castle
Walk through a dungeon beneath an old castle in search of a fabulous treasure.
http://www.daelindor.com/

Dark Awakening
Face ghosts,demons,and the undead.
http://darkawakening.homestead.com/enter.html

Fugitive Hunter
You are a criminal investigator searching for a fugitive. Ends with an ad for fcfjobs, but it's still a fun game. Useful action words not mentioned in the help: examine, check, mail, fingerprint, tattoo.
http://www.fugitivehunter.com

Get Tiffany
Free online multiplayer game about four guys trying to win the favor of a girl named Tiffany. Includes a chat, forum, member profiles, and help. [Requires Shockwave.]
http://www.gettiffany.com/

Gorgolon
Partake in this magical sci-fi game set in the greatest underwater civilization since Atlantis, Gorgolon. A Dan Zen game.
http://www.danzen.com/gorgolon

Hexmaster's Futhark
Web based adventure.
http://www.hexmaster.com/futhark/

Holo
A graphical adventure based on a virtual being that was created from the radio waves that surrounds the Earth. Includes an interactive game with each episode.
http://kallisto.com/holo/hindex.html

Interactive Stories
Interactive writers may participate in on-going science fiction story, 1000 Years On Planet Earth or the romance parody, Birds of a Feather Smash Together. Stories have run continuously since June, 1, 1999.
http://wvu.org/interactive-stories.shtml

The Interactive Story Web Ring
This is the list of Interactive Fictions web sites contained in the Interactive Fiction Web Ring.
http://g.webring.com/hub?ring=interactive

Monster By Mistake Online Adventure
Walk through the 3d animated sets uncovering cool games and activities.
http://www.monsterbymistake.com/

Mutiny on the Bounty
A Free educational Game based on the Mutiny on the Bounty and life in the eighteenth century. Adventure, logic, puzzles and prizes.
http://www.geocities.com/~jlhagan/A_Bounty_Game/

Online Mystery Games
Online mystery and detective games.
http://mysterygames.50webs.com/

Our Story
Interactive fiction resource for writers. Members may write a new open-ended story, or write an addition to an already active story.
http://ourstory.freeservers.com/

Skoolrush
Shockwave game with a school theme. Offers top scores list, icon sets, and credits.
http://www.skoolrush.com

Sleuth
Sleuth is an open-ended, detective role playing game (RPG) where players solve mysteries by searching for clues, questioning suspects and interviewing witnesses. Every mystery is unique with different victims, suspects and clues.
http://www.playsleuth.com

Something Amiss
A free online adventure game about a woman who undergoes a routine MRI scan and enters a strange new world.
http://www.somethingamiss.com