As announced, for Winamp users, Plastic Tunes now works with the "Now Playing" plugin.
The "Now Playing" plugin offers few advantages: it doesn't need other applications in order to work, like curl for AMIP, and it is easier to configure. Theoretically it can also insert more songs at a time into the database instead than one at a time, although this feature has not really been tested with Plastic Tunes yet.
On the downside, Now Playing does not notifies when a song is replayed after being stopped, which causes Plastic Tunes to incorrectly report the player as not playing when it is playing the same song. It is a minor problem, but there are no workarounds so far.

On the Plastic Tunes page is the new version.