Streaming media
From MozillaZine Knowledge Base
Normally Firefox deals with multimedia files (for example, .wmv and .mpg files) by first downloading them, and then launching the media player. You can get Firefox to stream multimedia, as Internet Explorer does by default, by using the DownloadWith Extension. After installing the extension, use the sample downloader settings that correspond to the multimedia player(s) you use. Alternatively, you can use the Launchy extension.