I'm currently developing 2 games, both of them my own, and both of them online.
One is the cliche overused zombie shootan, even though I still haven't seen a very adequate MMO with the same concept.
The other is based around exploration, set in a fantasy world where even the monsters are undiscovered, and are added to your adventure log, which you can take a look at for information on each monster. The map is streamed to the client via server, so the map could be ever-changing.
If you would like to test, or would like more info on either, you can comment here or email me at firstname.lastname@example.org