[costmo]

CarbonFin Outliner will definitely do what you need. It's a very simplistic outlining tool that has a few annoyances in its UI implementation (I can't wait for OO for iPad!), but works well and can email OPML files that can be opened in OO.

One thing to note is that, if you don't have any items checked in CarbonFin Outliner, when you open the OPML file in OO, the items are not in a check box type (they appear as non-checkable list items instead). I don't know if the cluprit is CarbonFin or Omni -- it's just a behavior that I noticed.