Recently I've stumbled upon an impressive collection of video walkthroughs for all levels of Rise of the Triad (shareware episode and Extreme Rise of the Triad included, plus a few extras):
http://www.youtube.com/user/Psychedelic ... pqPBku8YvQ
All videos are supplied with interesting and witty comments, listening to which makes a great entertainment in itself, apart from the walkthroughs that are rather detailed and in most cases cover all of the secret areas within a particular level. These videos are probably the number one source of in-depth information about the game alongside with the official FAQ. Apparently, the guy who did these videos is a prominent member of Something Awful.
As an undeniable confirmation of quality of this video collection, Joe Siegler himself gave it his delighted approval.