Action Items: Is there a feature to export to Excel a list of Action Items (under a specific project or all Action Items created by me)?
Out-of-Box portlet and Organizer option do now allow that. You could try to build new portlet based on Actionitem object. It would be easy assuming 1-2 hours of work.
What you could do is create a tab on your overview page and add the action items portlet. The portlet items can be exported to Excel from there. To do this just:
1 go to manage my tabs and add a tab (call it action items if you want)
2 Click on the properties of that tab and choose content
3 Click Add and find the Action items Portlet
Another option would to be to make your own portlet
1. Go to Admin > Portlets > New > Grid Portlet
2. Give it a name and in the data provider field choose 'Action Item System Data Provider'
3. Choose the layout and filter fields you like and save it
4. Place it on the tab you made