I would like to write a web application in which users can record short audio from within their browsers and stream it to my server. I understand that this is not (yet) possible using pure html, so I need to use a technology such as flash.
What are the alternatives I can use and which benefits/drawbacks to they have? Are they supported on mobile platforms (iOS, Android) as well?
Please give links to further reading on how to get started with each technology with regard to audio-streaming.
Capturing and streaming should be considered separate portions of this project. Flash (or Flex) would definitely be the right choice to capture audio. It's a fairly simple project for a freelance Flash developer, AS3 includes some classes that help you access microphone devices. See these resources for some (technical) information: Flex 3, Kirupa, Evolve, Techie Zone. After you capture it - you can stream to multiple devices via packetized RTSP/RTP (e.g. with an "agnostic" CDN like NetroMedia).