Updated everyday or so (2011/07/25). Under sea glass palace, glass castle in the sky full of waterfalls, trees in the sky. Working on a city SW of the glass structures, you can take mine cars there or most anywhere that is developed. Testing Lab in the city with lots of pistons stuff, including a duplicator. Two automatic 3 line train stations, more to come.
There are a number of dwellings (over 200 placed beds) in most explored places containing at least a bed and crafting area, most have multiple beds, multiple furnaces and storage. Some very large structures are now developing.
This would be a good base for an adventure map.