VideoLAN - VLC media player

Matt F. pointed out this is a cool (and free) way to stream media.

VLC media player is a highly portable multimedia player for various audio and video formats (MPEG-1, MPEG-2, MPEG-4, DivX, mp3, ogg, ...) as well as DVDs, VCDs, and various streaming protocols.

It can also be used as a server to stream in unicast or multicast in IPv4 or IPv6 on a high-bandwidth network.

It doesn't need any external codec or program to work.