http://www.on10.net/blogs/benwagg/Low-Latency-webcasting-with-Windows-Media-and-Siverlight/
Of course, Ben Waggoner is answering to this one.
I would like to add just one little addition, it is possible to acquire even shorter latencies with techniques used in ConferenceXP product.
Source codes and executable of ConferenceXP are available at MS Research web.
We have gained 300ms latencies, using our encoders and players build on top of WMF.
