I have always wondered why RIM has not provided an API or functionality in their Twitter, Facebook, and IM clients to share what you are playing in the media player. I know that BlackBerry Messenger can share what you are playing automatically but you cannot choose to share a specific song.
BBTweet Media Player fills that gap by letting you post #nowplaying tweets to your Twitter account while you listen to each song. The main downside is that they could not just add this functionality to the built in native media player but instead had to recreate a whole other media player.
I really hope RIM notices this app and opens up an API for the media player so it can be integrated in all the social apps. You can pick up the BBTweet Media Player beta at this link