Today Adobe announced the next version of Flash Media Server, FMS 3.5. Dynamic Streaming makes it easier to deliver a consistent stream even when bandwidth conditions and general network health changes during playback. While similar techniques were possible before it is now even easier and in particular much more seamless to integrate this functionality.
The DVR feature is great when viewing live streams, either to rewind back to the beginning of the broadcast or simply to re-view a certain part of the stream. I can see this being a great feature for sports broadcasts in particular.

FMS 3.5 now also ships with an in-built web server in the form of Apache. This allows developers to provide a single point of access to their content and they can now deliver SWF, JPEG, CSS, JS and other assets including video over it. It's notable that both RTMPT and HTTP can co-exist on the same port (80) and IP address.

Kevin Towes has a full length post on his blog outlining all the new features in FMS 3.5.