I often create accounts that end up in databases in UNIX crypt() format, so I have to copy the plain text password to the clipboard, paste it somewhere else to encrypt it and copy&paste the result to the database. An appropriate right-click function could make this a lot easier.
To achieve maximum flexibility, my favorite approach would be a plugin interface allowing external DLLs to add entries to the right-click menu.
The plugin interface could work like this:
Password Safe scans a specific directory (such as "plugins" in the application's installation directory) for DLL files. Each DLL is loaded and initialized with a call to pwsafe_plugin_initialize(). This function returns a pointer to a linked list of structures, each of them describing a feature provided by the plugin:
Context for that feature (e.g. PWSAFE_PLUGIN_RIGHTCLICK)
Name of the feature (e.g. "Copy crypt() password to clipboard")
Callback function (the parameters of that function should depend on the context)