I herd about RED5, but unfortunately I can't find any examples for feeding it with external source. I know RTSP is in development, but I'm thinking about (named) pipes or something like this. There is is also project named xuggle that is as far as I understand ffmpeg wrapper for Java, but I herd they have also problems with live streaming.
Depends on what you're trying to accomplish. If a simple 1 to 1 connection is all your after you should check out adobe's free peering system stratus: http://www.flashrealtime.com/tuts/p2p-in-flash.html . But if your looking for one to many broadcasting its going to either take a bunch of money for an fms license or a lot of poking around in red5 or RMTPD
WOWZA is a well-known commercial solution.
They claim better performance and price than FMS.
There is always of course the Free and free ffserver too! There's nothing wrong with 'streaming' using progressive download of FLV.
Try 3B NEXUS www.3bnexus.com. free rtmp flash player, simply add rtmp link and file key and embed to your site or add to playlist. We use their live streaming platform for internal comms.