Real Player is a commercial streaming audio/video solution. A competitor to WindowsMedia et al. Check it out at http://www.real.com/.

RealPlayer clips usually end with .RM or .RAM.

There is a RealPlayer for Linux; alternatively you can get MPlayer and it can link to the RealPlayer libraries and play Real clips with that.

The best news from Real for a while is the announcement of the HelixCommunity: http://www.helixcommunity.org/

SimonCrosby: RealOne? is a disgustingly bloated piece of software - full of features you don't want but Real wants you to use, such as content channels/browsers or whatever. RealPlayer forced MatthiasDallmeier to reinstall Windows after it highjacked all the default settings.