One of my favorite apps on the Palm Treo was an outline program called "Bonsai" by Natara, that allowed note taking in outline format. I think in outline format, and used that app more than any other. There were half a dozen or more competitors that also offered outliners.
I haven't been able to find an outliner for the BlackBerry. Natara is working on one for the iPhone, but not the BB. (That makes no sense to me; the BB has an established reputation as a business tool and an outliner is great for business people, but go figure.) Has anyone else come across one?