What is the best format for streaming audio that will provide the best quality/size and widest compatability? So far I know of

1. HE-AAC
2. MP3
3. WMA
4. Ogg
5. Real Audio

Now, I know that the best compatability-wise is MP3, but it isn't the most efficient at low bitrates. The best at low bitrates is HE-AAC, but I'm unsure of it's compatability. One question: is Windows Media Player automatically installed on Macs? Will the current version support the format used by most streaming audio?

Also, what should I know about licensing? Ogg is obviously free to stream, but I'm not so sure on the rest.

Not WMA or Realplayer, propritary. Causes to many end user headache's.

I haven't been able to get RAM to work on Foobar. At least not easily. I really like OGG. I think it sounds subjectively better than MP3. It plays on Foobar. I like many of the OGG streams at Icecast.

he-aac , can be used in rm container as well (for a home-solution i would still go with vorbis though).

I would go with Vorbis or HE-AAC ;-D. I personally listen to lot of Vorbis streams. A lot of streams are between -q 0 and -q 2 and subjectively sound very good, i.e Streaming Soundtrack's.com. I usually listen with a pair of Sennheiser PX250.

No one mentioned flash audio?

Audio-Streaming formats in a simplyfied nutshell (asuming a 64kbps stream):

- HE-AAC: high quality, low compatibility
- OGG-Vorbis: Medium-high quality, medium compatibility
- LAME: Low quality, high compatibility

Sure, there are other formats as well, but IMHO only the above three are really interesting for audio.

It depends which audience you have in mind.

For newbies, HE-AAC is almost the same as OGG IMO. And I do think HE-AAC does a great job at these low bitrates, i used to listen to somes radios with songs encoded with this format. I was using winamp.

So, if you are into OGG or HE-AAC, I would suggest the second.

Unless, of course, you want the most common computers in the world to play the stuff back conveniently.