Adding onto the closure of The Coven late last year (1999), they have
released their two commercial Quake and Quake II add-ons for free. Thanks Anthony for the info.

Here´s the scoop on the two add-ons, as well as the download information:

Full version of Disposable Heroes: was an unique multiplayer add-on for both Quake and Quake II, featuring new maps, mods and skins for both games.
Quake
http://www.thecoven.com/dhdlq1.shtml
Quake2
http://www.thecoven.com/dhdlq2.shtml

and

Full version of Deadlode II brought Team Fortress style gameplay to Quake II, as well as adding innovative new features such as fully customisable player classes and a modular construction system.
Quake2
http://www.thecoven.com/dl2dld.shtml