I've been using ZumoCast for quite some time now and like it. It's been stable on my Windows XP HTPC and streams to my iPhone and iPad are great. It transcodes all kinds of formats on the fly. I've yet to see an encoding or format trip it up.
One feature I quite like about it is it'll transcode and store the stream to the media on my phone. So I can set it up at night, on my phone, to bring down a bunch of transcoded video files and have my own in-flight entertainment on the plane in the AM.
It should also let to stream when you're off of your home network but I don't ever use that feature.