Now it is common for online services or social networks to show what music friends are listening to, but when I wrote this program in 2002 it was a bit more novel.
This was back in the days when people cared about AIM profiles, enough at least that if put a link there, it was likely that friends would see it. There was a program called HyperInfo which was just a tiny web server where you could host a profile with additional features (muliple pages, click tracking, replacing commands like username/ip with dynamic values).
The program I wrote checked if Winamp was open and if it was, it would extract the artist and song title from the window title, and then replace the {winamp} command in the HyperInfo profile with the song info. It also added a link to to AudioGalaxy (a much different service then than now) to instantly download the song. Simple, but pretty neat.