PC-games: this is not the site for you!!! Try Happy Puppy, Mad Cheat Page or this massive one.
*** Games and emulators ***
Spectrum - only one place necessary: The fabulous World of Spectrum, run by Martijn van der Heide. This site has the largest number of adventure games for any computer anywhere on the net!
Commodore 64 - have a look at Ben Castricum's C64 Internet Archive. The Electric Mayhem is definitely the best place for rare adventures. Or try The Commodore Zone.
Apple II - Asimov's the place for you. Has lots of adventures.
BBC - The BBC Lives here, and although emulation is a bit more troublesome than with most other computers (due to the lack of readily available BBC ROMs), it should be worth the effort.
Amstrad CPC - this site has lots of interesting adventures, including the infamous Philosopher's Quest.
The Interactive Fiction Archive - Volker Blasius does a tremendous job of maintaining this site dedicated to all sorts of adventure games.
Adventureland - Hans Persson is trying to gather information on each and every text adventure ever released. And he's doing a very good job, too!
Paul Doherty - a very nice German guy maintaining a site which has links to Infocom, Level 9, Magnetic Scrolls and more. Also contains free Scott Adams games and interpreter.
Spectrum info can also be found on Ian Preston's now discontinued, but very interesting site.
Emulate! is a neat Speccy e-magazine run by Barry Plewa
A C64 solutions page is being handled by Martin Brunner.
The C64 Game Guide, based in Sweden, is a great resource for game information, both for adventure games and other genres.
BBC (and adventure) interested people should definitely give the BBC Game Archive a try. It has lots of information on BBC adventures not found elsewhere.
The Commodore Wire will let you know what's happening on the C64 scene.
Stu Whyte a.k.a. The Balrog runs a terrific site about Amstrad adventures, including a complete list of every Amstrad adventure ever released!
Jim Groom has a site dedicated to Oric adventures, among other things - check it out!
*** Various ***
Adventure Probe is a fabulous printed magazine dedicated to adventure games. It is published on a monthly basis and features lots of reviews, hints, solutions and more for 8-bit computers. Give it a try! Contact: Adventure Probe, 52 Burford Road, Liverpool L16, 6AQ, United Kingdom.
Druadic runs an excellent map site which is frequently updated - check back every now and then for news.
Some of the solutions are zipped - try Winzip if you're at a loss.
Henrik Jensen has a nice site on adventures (and Star Trek and other things that make the world a better place :-) Unfortunately it's in Danish.