Glitch is still in early beta, and thus open usually only during the weekends. Nevertheless I got far enough in the game to get a first taste of the "endgame", which in Glitch is somewhat unusual: You work together with other players to open up new zones in the world. Basically you need to find a greyed out "street" and look in one of the neighboring streets for a "project", which you access at the vendor. A project consists of several stages, in each of which you can contribute either specific items, or labor. Usually you need specific skills for that, which is why I call it the "endgame", it's something to do when you are already further advanced.
Once all phases of a project are finished, the street opens up, and the world has grown a bit. Everybody who participated gets some rewards, although only the top contributors get a really big reward and will be listed on the streets loading screen.
I find that concept really interesting. Although the new streets don't offer anything fundamentally different from the existing ones, players over time can open up whole new regions. And building up the world feels satisfying, even if it isn't exactly "player created content". Players only perform set tasks to open up developer created content. Nevertheless the idea is neat, and I could imagine some interesting applications of that in a fantasy MMORPG.