[VTUrge311]

Here are some plugins for Winamp:

http://www.mlipod.com has a link for the M4P plugin which will allow you to play .m4a and .m4p files

http://www.etree.org/shnamp.html will allow you to play .shn files

http://www.winamp.com/plugins/details.php?id=131643 for .flac files

Winamp has had .ogg support for a while, just make sure you have the Full version, not Lite

I don't use Windows Media Player so I don't know about any plugins for it, sorry.