I've been playing Kingdom Of Loathing a lot over recent months. I'm nearly done with my second ascension (i.e. I finished the game and died, and got reborn, and have nearly finished it again).
It's... a web-based RPG that's free-to-play (though there is premium content), where all the graphics are stick people, just about all interaction is done via clicking links and things in menus, and it's all implemented in php, javascript and html forms. It's also several years old, but I only really discovered it about 2 months ago.
It's very tongue-in-cheek and funny; most of the time it's word-play and absurdity, a lot of the jokes are referential, some are just plain crude. I spent a lot of time just having fun reading battle text and descriptions of items.
And it's kind of an MMO but really not very at all. You don't really directly interect with any other players for the main core play of the game, you only really talk directly to others in chat (which is ever present but optional). There are clans and PvP but it's all optional. You can buy a shop in the mall or sell items through the marketplace to other players, so it does have an economy too.
All the same, it seems to have a friendly and active community, and it receives regular updates. It was even advertising a KoL convention and comic book coming out, recently.
Related links:
wiki,
fan site,
forum,
calendar,
foodstuff chart,
buffbot
