Given the limitations of 32kbps CBR, what LAME switches can I used to make a song sound the least crappy? I'm doing this for my webcast, which currently uses mp3pro 32kbps mono, but my concern is that people without the plugin installed are going to be hearing something worse than I could manage to do with some well-chosen LAME command-line switches.

Thanks.

would you mind switching to vorbis ?

If you have to use mp3, LAME is not the best choice for low bitrates. You'd get better results with one of the Fhg encoders.

You could try --alt-preset 32 -mm, but surely it wouldn't be sensationally better than the "core" MP3 part of a mp3PRO file, because at these bitrates standard MP3 is not competitive anymore. So you would basically trade a quite good mp3PRO sound (with SBR-capable decoders) for a significantly worse sounding MP3. In my opinion it's a better idea to make your listeners use the Winamp plugin from Coding Technologies (or the demo version of their codec), also because it is capable of decoding true internet streams, as far as I know.

I found a quite good commandline, It´s a bit more artifacted, but it has more high-frequences:
--preset cbr 32 --resample 16000 --lowpass 8 -mm
But I would use vorbis, it gives you a much better result. There is also a platform-independent java-player which can play live streams: http://www.jcraft.com/jorbis/ You can make on your site this typical applet-window like with wmp/real.
Winamp can play the streams also without any problems. RealPlayer/Helix will also support them in future and Tobias (the developer of oggds) is working on a icecast/shoutcast-source filter, that means all DirectShow-Players like WMP will support them, too.

Try MUSICMATCH mp3PRO! 32 kbps 32 kHz, j-stereo
It's the best around this bitrate

I'd use Vorbis if I could, but I stream through Live365 (mostly because they take care of all the royalties and keeping the station legal), which is an mp3-only deal. My understanding is that there are no freely available FhG encoders, is that correct? As I said, I'm already using mp3PRO (32kbps 44khz mono, to be specific)....so I might just end up sticking with that.

Thanks for your help!

MusicMatch "Bloatware" Jukebox includes an unlimited FhG FastEnc/Alternate encoder (MP3Pro support is limited though).

IIRC, the "normal" setting (FastEnc) is supposed to give better results at low bitrates than the medium/high (Alternate) settings.