With the tagline "Instant adventure gaming" Sarien.net gives you that old school adventure game feeling from classics such as Police Quest, Leisure Suit Larry and Space Quest.

Not only does it feature (at the time of writing) three such games, ported to JavaScript, but the author, Martin Kool, throws in a bit of multiplayer fun. As you play through the games and interact with the different scenes and objects, you will meet other people walking around the same game world and doing the same things. A very nice touch and a great way to bring a bit of innovation to the games (as if simply making them in DHTML was not impressive enough).

And for the icing on the cake, the engine and a demo game is available on Google Codeand (under the LGPL license) and there's a game resource exploration tool called Sarien Studio available online for the technically interested.