I ditched WinAmp awhile back, so I've been using IrfanView to listen to Phone Posts made in .ogg format. It works but I don't use the program much otherwise, so I decided to go looking for plugins/filters to open Ogg files from audio software I more frequently use. A quick trip to Vorbis.com pointed me to CoolEdit Ogg Vorbis File Filter, Xiph Quicktime Components, and Ogg Direct Show Filters for Windows Media Player.
So far, I've used the CoolEdit plugin for radaromalley's latest two Car Karaoke posts and it's seamless. I am very pleased.
edit 5 April 2006: updated the URLs for the WMP and QT plugins.