Eclipse toolbar and menu bar group action id's

ICommonMenuConstants

IWorkbenchActionConstants

IIDEActionConstants

Few examples:
"group.new"
"group.goto"
"group.open"
"group.openWith"
"group.show"
"group.edit"
"group.reorganize"
"group.port"
"group.generate"
"group.search"
"group.build"
"additions"
"group.properties"

These will be used as a insertion points if you are contributing a new action/menu action/toolbar action.