OK,
Ogg-FLAC is only FLAC contained in an Ogg layer, the FLAC project joined Xiph.org in 2003 so is natural that FLAC is going to use Ogg as a transport layer (container) and is natural that the extension of Ogg-FLAC will be ogg, Ogg is only a container used first by Vorbis, and now used by FLAC and Theora (a video codec). I'm not sure about Speex.
This type of files are realively new and not all the player can reproduce them, but is to be expected that slowly being fully adopted, the only player I know that can player them is foobar, but no the official the updated one:
http://www.saunalahti.fi/cse/foobar2000/you can use the oggcodecs for play them without problem in any directshow player to:
http://www.illiminable.com/ogg/you can still using the native FLAC, at least when more and more player can reproduce them.
the iRiver supports only Ogg Vorbis, when some software/hardware said that play Ogg generaly it refers to Vorbis, maybe because they dont know that are various codecs that can be contained in ogg, or because they dont know that Ogg is only a container (like matroska)
I hope that everything is clear now