If one has time to waste

Crimson Room: http://www.datacraft.co.jp/takagism/index_e.html

Viridian Room: http://www.fasco-csc.com/works/viridian/index_e.php

Anode & Cathode: http://www.anodeetcathode.net/office/

Mystery of Time and Space: http://server-admin.pwp.blueyonder.co.uk/motas/mystery/nochatgame.htm