Kendo - 4:49 pm on May 28, 2012 (gmt 0)
First you need a media server and today there are lot's of free streaming services. Search for "free conference streaming" and you should find lots of options. Their services are quite sophisticated, enabling you to create one or more channels, and they will provide free encoding software. Their encoders will enable you to stream to a Flash media server and you should be able to get encoder software for Macs, because they have used Flash throughout.
Next you will need a camera, and here you have to be careful to check that the input ports are suitable for the encoder. I used to use a couple of cameras for live events using DV outputs (don't actually recall the port type) but the newer cameras don't have these ports any more. So before you get yourself a camera download the encoding software and read up on which ports can be used.
Then you'll need a decent Internet connection to stream. You can lower the bitrate on your stream but you need consistency. Also, consider your users as some may only get 500 k/sec, and even on higher speed networks they do get overloaded. There's nothing worse than watching something that lags.
What I do recommend before committing any cash is to set up a free streaming account and then borrow a camera. Don't try to save a backup while streaming because your notebook will be lucky to provide the memory resource just for the stream. Backups can be created on the media server end.
If you end up with a stream service that has a free threshold and charges thereafter, please be aware that whatever bitrate you are providing to one user, you can multiply for ever extra user... so 1.5 Mb/sec x 100 users = 150Mb/sec!