Twonky Beam is the latest product from the minds of Twonky Media. Twonky Beam is a free plug-in for Windows Internet Explorer 6 (and more current versions). I've been using it for the last week with my Sony Bravia LCD 40W5500. In short, Twonky Beam allows you to stream audio & video media straight from the browser to connected DLNA/UPNP devices in your home.
It's pretty sweet.
If you are a die-hard Firefox user, you'll have to wait a bit (support for other browsers is coming very soon), but definitely check this out: