create a hello world plug-in in eclipse.
1. if you want to add a menu after “Edit” menu, change the path to “Edit”
2. if you do not want to set the menu location in eclipse main menu, just
leave it empty or set it to “additions”
3. if you want to add this action to “help/helpStart”, change the menubarPath
of “Sample Action” to “help/helpStart”
4. if you want to add this action to “file/import.ext”, change the
menubarPath of “Sample Action” to “file/import.ext”
5. if you want to add this action to debug action set in main toolbar, change
the the toolbarPath of “Sample Action” to
“org.eclipse.debug.ui.launchActionSet/debug”
then if you start the plugin, and try to drag debug action set, the “Sample
Action” will move with the debug action set
6. if you want to add this action to debug action set in main toolbar, change
the the toolbarPath of “Sample Action” to
“org.eclipse.debug.ui.launchActionSet/external”
then if you start the plugin, you will see the “Sample Action” and debug
action set seperated with a separeator,
try to drag debug action set, the “Sample Action” will move with the debug
action
7. if you want to add this action additions set in main toolbar, change the
the toolbarPath of “Sample Action” to “additions”

then if you start the plugin, and try to drag debug action set, the “Sample
Action” will not move with the debug action set

In one words:

A complete menu path is simply “menu name/group name.”
A complete toolbar path is simply “action set ID/toolbar group name.”

org.eclipse.ui.menus

http://help.eclipse.org/helios/index.jsp?topic=%2Forg.eclipse.platform.doc.isv%2Fguide%2Fworkbench_cmd_menus.htm
Menu and toolbar paths

http://help.eclipse.org/helios/index.jsp?topic=%2Forg.eclipse.platform.doc.isv%2Fguide%2Fworkbench_menupaths.htm
Eclipse Platform Extension Points

http://help.eclipse.org/indigo/index.jsp?topic=%2Forg.eclipse.platform.doc.isv%2Freference%2Fextension-
points%2Findex.html