Plastlets are small Plastic applications that do very simple tasks and respond to messages from other Plastic-enabled apps. What makes them distinct from normal Plastic applications is that they are small and intended to be bundled with other applications rather than stand on their own. A Plastlet is smart enough to recognise when it has already been registered by another parent application, so they can be safely bundled with many applications without the user having more than one instance registered with the hub. The point of plastlets is that if you expose common non-applicaton specific functionality as a Plastlet, then all other Plastic-enabled apps can benefit from it too.
Currently Plastlets exist to expose common desktop functionality (through JDIC):
Any Plastic-enabled application that is capable of sending the standard load messages for VOTables and FITS files can use these Plastlets.
At present Plastlets are bundled into the beta version of the AstroGrid workbench (though they are disabled by default and need to be enabled using the Plastic/plastlets menu). They are also available from a webstartable Plastlets container.
The Javadoc and source code for the Plastlets library are available from the links to the left. The binary can be downloaded from the AstroGrid Maven Repository.