After Yahoo! Messenger 9 and Winamp 5, nearly all plugins listed on winamp.com claiming to display song status in Yahoo! Messenger were useless. None of them worked and even a google search became useless with all old plugins coming to picture. But not now.
I have finally managed to find a plugin which works with Winamp 5.54(latest at this moment) and Yahoo! Messenger 18.104.22.1689(BETA) (Latest at this point).
Plugin is called Yahoo! Messenger Now Playing plugin for Winamp
Not only it displays current song in Y! Status bar but also displays Artist, Title, Genre, Album, Year, Track Number, Progress bar, Song length, Bitrate, Samplerate, Channels, Volume, Playlist position, and Playlist length. It also supports all type of statuses – busy, idle and invisible. And on top of it does not have any advertising at all. You can configure the plugin via Winamp>Preferences>Plugins>General purpose>Yahoo! Messenger Now Playing 4.6(configure)