Some interesting pieces from Vorbis.com: new (1.0.1) versions of the Ogg Vorbis libraries; Icecast2 beta for streaming Ogg files; and IceShare for BitTorrent-style Ogg streaming and downloads.
There are two (official and unofficial) Ogg components for QuickTime, which should work for iTunes.
This is here because of Loca Records, and their copylefted Ogg audio files. Does RealPlayer do Ogg yet? MPlayer seems to manage alright.