
Massively considers a game to be in open testing if it has open, public signups and plans for a server wipe before its official launch. Self-described "open beta" MMOs that have soft-launched with functioning real-money cash shops will not be listed.
Knight Age (Joymax): Announcement, Signup (open beta 8/28/2012)
KULTAN: The World Beyond (Bigpoint): Announcement, Signup
Remanum (Travian): Announcement, Signup, /r/
Sevencore (gPotato): Announcement, Signup (gPotato OB begins 9/6/2012)
Soul Captor (Gamania): Announcement, Signup
S.T.A.L.K.E.R. Online (CyberTime Systems): Announcement, Signup, /r/ (Russian-only)

We consider an MMO to be in closed testing if it features either future test signups or an ongoing semi-private beta/alpha that cannot immediately and freely be accessed by the general public. Some are restricted by NDAs.
Age of Wulin (gPotato): Announcement, Signup (Asia, EU)
Age of Wushu (Snail Games): Announcement, Signup (US; launching 10/18/2012)
ArcheAge (XL GAMES): Announcement, /r/ (CBT5; Korean-only)
ArchlordX: The Chronicles (Webzen): Announcement, Signup
Born to Fire (Aeria): Announcement, Signup
Bounty Hounds Online (Wicked Interactive): Announcement, Signup
City of Steam (Mechanist): Announcement, Signup, /r/
Dawntide (Working as Intended): Announcement, Signup, /r/ (development on hiatus)
Dota 2 (Valve): Announcement, Signup, /r/
Dragon Born (KoramGame): Announcement, Signup
Dragon Crusade (Aeria): Announcement, Signup
Dragon Knights (Aeria): Announcement, Signup
DUST 514 (CCP Games): Announcement, Signup, /r/ (PlayStation Plus beta began 8/21/2012)
End of Nations (Trion): Announcement, Signup, /r/
Firefall (Red 5 Studios): Announcement, Signup, /r/
Forge (Dark Vale): Announcement, Signup
Glitch (Tiny Speck): Announcement, Signup, /r/ (back in beta)
Grecca (Banbox): Announcement, Signup (in "open" alpha)
Grimlands (gamigo): Announcement, Signup
Guns of Icarus (Muse Games): Announcement, Signup, /r/
Lime Odyssey (Aeria Games): Announcement, Signup
Line of Defense (3000AD): Announcement, Signup
Living After War (Alaplaya): Announcement, Signup
LotRO: Riders of Rohan (Turbine): Announcement, Signup, /r/ (launching 10/15/2012)
Maestia (Gravity Interactive): Announcement, Signup
MechWarrior Online (Piranha): Announcement, Signup, /r/
Origins of Malu (Burning Dog): Announcement (beta coming 9/30/2012)
Otherland (gamigo): Announcement, Signup, /r/
Path of Exile (Grinding Gear Games): Announcement, Signup, /r/ (open beta in August)
Pirate101 (KingsIsle): Announcement, Signup, /r/ (launching in 2012)
PlanetSide 2 (SOE): Announcement, Signup, /r/
RaiderZ (PWE): Announcement, Signup, /r/
Renaissance Heroes (ChangYou): Announcement, Signup, /r/
RIFT: Storm Legion (Trion Worlds): Announcement, /r/
Salem (Paradox Interactive): Announcement, Signup, /r/
SmashMuck Champions (Kis Studios): Announcement, Signup, /r/
SMITE (Hi-Rez): Announcement, Signup, /r/
Star Conflict (Star Gem): Announcement, Signup, /r/
Storybricks (Namaste): Announcement, Signup (in "open" alpha)
Taikodom (Gamersfirst): Announcement, Signup
Tamer Saga (PopAce): Announcement, Signup
The Missing Ink (RedBedlam): Announcement, Signup
The Mummy Online (Bigpoint): Announcement, Signup
The Repopulation (Above and Beyond): Announcement, Signup, /r/
The War Z (Hammerpoint): Announcement, Signup
Traveller AR (Ingz): Announcement, Signup (beta on hold)
UFO Online (gamigo): Announcement, Signup
Universal Monsters Online (Bigpoint): Announcement, Signup
Waren Story (Aeria): Announcement, Signup
WindSlayer 2 (Ignited Games): Announcement (beta closed down until fall 2012)
World Alpha (World Alpha): Announcement, Signup
War Thunder (Gaijin): Announcement, Signup, /r/ (fka World of Planes)
WoW: Mists of Pandaria (Blizzard): Announcement, Signup (launching 9/25/2012)
World of Warplanes (Wargaming.net): Announcement, Signup, /r/
Subreddit links helpfully provided by Steven Eyerman!
Betawatch is Massively's weekly report on the latest MMO alphas, betas, and other games still meandering toward an official launch. From ArcheAge to World of Warplanes, it's covered here, complete with sign-up links so that you too can perform the unpaid quality-control work otherwise known as game testing. Drop us a comment if we've missed one!