As long as you have an always-on connectiong + always-on computer (ie. you don't shut it down) then you can feed straight to LiveATC... since you already have a scanner I'm assuming, you can hook it up to your computer and it sends a very small amount to the server, and it's the LiveATC server that actually broadcasts the info.
Simply: you just stream the data to LiveATC, and Dave here does the rest.
If for some reason you're not looking to stream ATC feed, look in to shoutcast.