The Dungeon Master Friendly Initiative has been helping build the multiplayer experience since the NWN1.
Players
If you want to explore modules that are Dungeon Master friendly, start at the DMFI modules page:
http://nwvault.ign.com/View.php?view=NWN2ModulesEnglish.DMFM
If you're looking to be a DM for a session, check out the DM 101 module for NWN2:
http://nwvault.ign.com/View.php?view=NWN2ModulesEnglish.Detail&id=296
For more advanced topics on how to bring NPCs to life in a DM'ed module, see Carlo's article "Creating Believable and Memorable NPCs":
http://dmfi.slightlysilly.net/modules.php?name=Content&pa=showpage&pid=9
DM forum
http://nwn2forums.bioware.com/forums/viewforum.html?forum=117
Find others to play with at NWNConnections
http://www.neverwinterconnections.com/
Find others to play with at NWNCampaigns
http://nwncampaigns.com/
Builders
Builders who wish to make their modules Dungeon Master friendly can check out the following resources:
DMFI Developer Package
http://nwvault.ign.com/View.php?view=NWN2Scripts.Detail&id=38 Official
The Dungeon Master Friendly Initiative Guild:
http://nwn.bioware.com/guilds_registry/viewguild.html?gid=20
DMFI's Guide: Building a DM-Friendly Module
http://dmfi.slightlysilly.net/modules.php?name=Content&pa=showpage&pid=7