I'm surprised no one else has replied, so I will. This site is more for D2 OP stuff. Not that SFCIII isn't wanted, its just that SFCIII is mostly mods these days. The main traffic here for SFCIII is various mods announcing campaigns starting up, and announcing new versions of their mods that just came out. Most SFCIII discussion goes on at the mod sponsors web site.
For SFCIII, I've played the GFL mod called Legions at War. Its pretty good, not quite as good or as balanced as the creators say, but pretty good over all. Other mod called Alternate B is very popular..if not slightly more active. At least from what I've seen with the number of players on the different servers. I haven't played Alternate B, so can't really give you any more info on it.
As far as SFCII: OP goes, lots of exciting stuff going on. Check out the "The Dynaverse is one year old" thread.. some great news there! Also there is a campaign about to start. ATOKII
Just check out the various section for SFCIII and OP.. everything you need, you should be able to find there.