Nodiatis went live today, it's sort of like Runescape but for adults. It has an incredibly deep skill system and all the amenities you'd expect from an MMO:
Grouped Boss Raiding
Trading/Auctioning
Minigames for Resource Gathering like Fishing, Gardening, Mining, etc
Complex Crafting System
Unique PvP System
This game is not for the average player, it takes some intelligence to create a character that is truly great because the magic system is complex and the skill system allows you to build your character however you want. The game can be played in a browser, but it will also be available for download and categorizing it into the leper colony browser/mud forum would be an injustice. This game plays like an MMO. Try it out.
www.Nodiatis.com
EDIT: We did away with Adventure Time and replaced it with Rested Time. Now you can play all you want for free! You just level faster when you have Rested Time.