So, here we go! First post from scary old uncle TheAncientGoat ;)
Evidyon, MMO from Reddit-way
Evidyon is an interesting 3D MORPG recently gone Open Source under the advice of the reddit community, releasing a whole slew of content, tutorials and documentation of how they went about making it in the process. This is a very admirable move, we'll all agree, so show them some love. Unfortunately, it's windows only, relying on DirectX (not VB though, thanks for the fix Nerrad), and I haven't gotten it running under Wine as of yet, but hopefully a few smart alecs can help port it.
Like most other mmo's it has a fantasy setting, as you can see in the screenshot and video, it also sports a Diabloesque style of combat
HackWars: MMO where you craft by programming
This was also found via reddit and the author wrote some pretty interesting commentary on developing such a game (which you'll see if you follow that link). Also, why not post upcoming FOSS games on our little corner of redditOpenSourceGames and we'll try and cover them if we have the time.
SlothRPG is a fantasy 2D MUD -like RPG, also written in Java. It has recently been re-invigorated, so it's worth checking for updates. Unfortunately it doesn't have any servers online at the moment, so you'll have to host your own if you want to check it out