There’s a renewed interest in Gaia Online, which is interesting to observe. Gaia has been around for a long time, so when the meme that casual and massively multiplayer games could be the next big thing, Gaia gets put in the spotlight as an example of a Casual MMO that is doing well.
To that list you can add all the browser based MMOs, like torncity, kingdom of loathing and travian, of course. However, Gaia is kooky and squarely aimed at the tweeny market, and that seems to be how Casual MMOs should be perceived.
There’s one recent interview floating around, here, but if you’re interested in the technical aspects of running an lightweight MMO like Gaia, you can do worse than read through this thread about the customisation of phpBB by Gaia Online. It’s only going to be of interest to other developers, but you can see how far back Gaia stretches. The thread is from 2005 and the developer was already caching and rewriting custom code to keep up with the load. It’s obviously a very familiar story for anyone who has built or maintained websites that get hit with viral bursts or sustained high levels of traffic, but it’s interesting nonetheless.
And, if that doesn’t interest you, then consider this - you’re not an MMO until you can fish. Fact.