Wikipedia sometimes has some hiccups. I think most in the fold will agree that SOF and SF are not the same thing. SOF is considered to be a more specialized force both in terms of capabilities and in employment. Special forces, while quite capable in their own right, are generally a larger force supporting SOF or conducting operations on their own in support of more generic combat forces.
Ex of SOF: Element of 22SAS, JTF2, SFOD(D), DEVGRP, TAG1(I think 1 is, AUS SOF)
Ex of SF: Para, Rangers, Green Berets, Marine Recon, Spetznaz, TAG2(AUS SF, I think I got the 1-2 thing right)
I've probably got the Aussie TAG's mixed up or something, but I think that's the general idea (of course, corrections to all above are invited)
As well, I've only seen SOC to refer to a unit's capabilities, as in a spec ops-capable unit. An example would be a spec ops-capable Marine Expeditionary Unit, or MEUSOC.
Cheers,
Duey