PMC has released WRP technology demo terrains containing 5 desert terrains. This was the intial real terrain work for ArmA and we did it in PMC Tactical forums ArmA editing area at PMC ArmA WRP Tutorial topic.
PMC released empty WRP files for 102km and 204km terrains. These are mainly meant to help terrain developers to quickly get large terrains in-game using WrpTool. These aren't really playable terrains, unless you of course want huge terrain with 0 objects.
This is 25km x 25km sized terrain in similiar theme to Everon and Nogova. It was first released back in OFP and had great success as many people liked the massive size and yet detailed look with interesting locations etc.
Check PMC Addons/Mods Manuals: PMC Rugen.
This is 25km x 25km sized terrain for desert environment. It was first released back in OFP and was used a lot in PMC missions.
Check PMC Addons/Mods Manuals: PMC Rattler.
All OFP "islands" joined together, except Nogova. The name comes from the BIS used island names of Abel, Eden and Cain. This was the first and true original "OFP World" which many have copied.
Check PMC Addons/Mods Manuals: PMC AEC.
This is 51km x 51km sized terrain with war torn cities, couple of modern cities, harbors, oilfields and two airfields.