I just stumbled into yet another roadblock to the free software alternative to MP3, Ogg: QuickLook fails to preview ogg vorbis files. I knew QuickTime would play Ogg Vorbis after installing the XiphQT component so I installed that. Still, no QuickLook previews for Ogg Vorbis. I now had a mission.
I started with a google search for quicklook and ogg, nobody seems to have written a QL plugin for ogg yet. I ran across a few blog posts about adding text types to TextEdit so that they could be previewed by QL and thought to myself: can this be extended to QuickTime? One short patch to QuickTime's Info.plist later and I found out that it could!!
Append the following above the last 2 lines of your QuickTime's Info.plist (the last 2 lines are </dict> followed by </plist>), save it, then move QuickTime out of your Applications folder and into a folder *not* in the Applications folder hierarchy, then move it back. Problem solved!
<key>UTExportedTypeDeclarations</key>
<array>
<dict>
<key>UTTypeConformsTo</key>
<array>
<string>com.apple.quicktime-movie</string>
</array>
<key>UTTypeDescription</key>
<string>OGG Audio/Video file</string>
<key>UTTypeIdentifier</key>
<string>org.xiph.ogg</string>
<key>UTTypeTagSpecification</key>
<dict>
<key>com.apple.ostype</key>
<string></string>
<key>public.filename-extension</key>
<array>
<string>ogg</string>
</array>
</dict>
</dict>
</array>