This add-on could be used with MediaMonkey v2.0 or higher. It allows adding of the currently played/selected track(s) to the specified playlists using hot-keys or toolbar buttons. You could specify several playlists for adding tracks, each one with its own hot-key and toolbar button.
Download:
http://solair.eunet.rs/~zvezdand/AddTra ... aylist.htm

What is new:
v1.1.1 - 2012-02-06
* Fixed: option to use static playlists which are children of some auto-playlist.
v1.1 - 2012-02-04
* Added: option to add arbitrary number of playlists, each one with its own hot-key and toolbar button;
* Added: possibility to specify playlist that is not on the first level without specifying its full path (only if a playlist name is unique);
* Fixed: adding of selected tracks [MM2].
v1.0 - 2012-01-22
* First public version.
Installation:
* For MediaMonkey 3.0 or higher - just double-click on the AddTracksToPlaylist-xx.mmip file; if you are on Vista or Win7 and you got "Product installation error", make sure you have MM3 set to "Run as Administrator"; if you downloaded the installation package with IE7 and it changed its extension to a .zip, you should first change it back to a .mmip.
* For MediaMonkey 2.x - rename a .mmip extension to a .zip, extract the AddTracksToPlaylist.vbs file to the MediaMonkey's "Scripts\Auto" folder and restart MM program.
Usage:
Choose Add Currently Playing Track to Playlist option from the Tools | Scripts menu if you want to add the currently playing track to the specified playlist or choose Add Selected Track(s) to Playlist if you want to add the selected track(s) to the specified playlist. You could also click the corresponding toolbar button or press the predefined hot-key. The toolbar buttons are located at the Add Tracks to Playlist toolbar in MM4 or Standard toolbar in MM2-3.
The default hot-key for adding the currently playing track is Ctrl+Alt+Shift+0 and for the selected track(s) is Alt+Shift+0. However, you could change the hot-keys in the Tools | Options dialog box on the General > Hotkeys sheet specifying General: Execute script: Add * Track to Playlist in the Action combo box with the wanted hot-key pressed in the Hotkey box. You should also use that step if you want to make the hot-key global since the default hot-keys are valid only when used inside of the program.
The playlists to which you want to add the currently playing or selected track(s) should be specified in the Tools | Options dialog box on the General | Add Tracks to Playlist sheet before you choose some of the previous options for adding tracks. You could directly select a playlist from the combo box only for playlists on the first level, i.e. a playlist which is a child of the Playlists node. If you want to add tracks to some nested playlist, you could do that if you manually enter a full path to that playlist using "\" as a separator between nested levels, e.g. Favorites\Selected Tracks. This also means that such playlists cannot have the "\" character in their names. However, if the wanted playlist has some unique name, then you could specify it without its full path.
The Add buttons next to the playlist combo boxes allow adding of arbitrary number of playlists. Beside of the each added playlist is the Del button which allows removing of the adjacent playlist from the list. The first two initial playlists cannot be removed. The default hot-keys for newly added playlists are Ctrl+Alt+Shift+1 till Ctrl+Alt+Shift+9 for currently playing track and Alt+Shift+1 till Alt+Shift+9 for selected tracks.
You could add more than 9+9 playlists, but if you want to have hot-keys for those with the number in menu greater than 9, then you need to use the Hotkeys sheet to specify them. You could add tracks to the newly added playlists by click on the corresponding toolbar button or by press on the default hot-key immediately after you confirm the settings in the Options dialog box, but you need to restart the program first if you want to change the hot-keys.