If you're interested in new stuff, try making your own. It's easier than it sounds!
I'm starting a series of weekly tutorials. Check it out
here.
Anyways here's that list.
Campaigns:
Outpost: Renegades (demo)
Outpost: Second Chance (in development, demo available)
Colony Games:
Plymouth Cold War (buggy)
Various minor projects
Multiplayer:
Greenworld/Greenworld v2 (tileset + maps)
Survivor (various)
Miscellaneous
Various new LoS/LR maps
Outpost: Second Chance (in development,
really old demo available?)
Survivor:
To The Skies or To The Grave (forgotten)
Forsaken World v1 (lost)
Dead Zone (forgotten)
Caught in the Crossfire
Forsaken World v2 + 5P version
Judgment Day
"Bad Day on New Terra" (unnamed, in development)
Misc. Multiplayer:
Swarm/SwarmZ
Scout Rush
Doomsday
Bomber's Big Blast
Scout Rush 2 (scrapped, redevelopment pending)
Halloween Special (fun in theory, sucked in practice; demo available.)
Cold War (3P version only; still waiting on 6P version.)
Edit: There are also some new things for OP2 that aren't new levels:
Color Mod 1
Color Mod 2
Color Mod 3 (in development)
Difficulty Mod 666/DM666Z
NetFix