xmmstcl lets you control XMMS playback, skip, pause, change the playlist, change skins, and do everything else provided by the xmms_remote_* methods, which is almost everything from the standard user interface.
xmmstcl plugin also has some things not available there, such as "XMMS onchange" which lets your Tcl/Tk application know when something happens in the player. The companion "TkPlayer" has samples for the most important functions and will keep XMMS busy by generating random playlists with songs that you haven't heard in a while.
With this extension, you can:
require package xmms
xmms playlist [glob /music/mymp3s/*mp3]
xmms position 5
All from the convenience of your favourite tcl-enabled application (this webserver, for example). It provides all of the xmms_remote_* methods (xmms-1.2.5 version, 1.2.7 adds two extra).