Actually I've been thinking about letting people call-in through a VOIP program like TeamSpeak. Listeners could "call-in" by connecting to your TeamSpeak server setup with with moderated channels so a "call screener" could screen incoming "calls" while you're in a DJ/monologue session and then patch them through when you're ready. A client in the "On Air" channel running on the server would then send the resulting audio in the channel through a Virtual Audio Cable to the Voice FX plugin. You can download the Voice FX plugin http://www.winamp.com/plugin/voice-fx/128792
and DSP stacker plugin. For the Voice FX plugin you would need to set the default recording/mic device in the Windows control panel to one of your virtual audio cables and set the "On Air" TeamSpeak client to the output of the same virtual cable. You can find TeamSpeak (or Ventrilo might be another option) on Google.com. It also might be possible to do with the same setup if the Skype client allows you to select a different audio device for output/input but I don't know anything about Skype so I dunno bout that.
Just thinking outloud so if anyone has a better idea (w/out using SAM Broadcaster) I'd love to hear your thoughts because I'm thinking about it.