Adobe has created an LLVM based C to Flash VM compiler. Their example
code includes the Vorbis library:
http://labs.adobe.com/wiki/index.php/Alchemy:Libraries
This should make producing a Flash Ogg/Theora player using the Theora
reference library a fairly straight forward process.
Such a player will never perform as well as native support, but it
would be highly valuable along side cortado (Java) as a fallback
mechanism.
Unfortunately I know next to nothing about flash development and have
no particular desire to learn, so I'm not offering to do this work.
But I'm sure that some people here do, or know people who do. Someone
with the right knowledge has an opportunity here to make a very
significant impact in the usability of free formats by developing a
drop-in flash based fallback for the HTML5 <video/> and <audio/>.