A writer in the Ecco group just posted urls to the following web-based outliners; interestingly, each of these outliners appears to have user definable columns:
http://www.ioutliner.com/
http://www.sproutliner.com/

I haven't tried either of these, but will play around with them soon.

Daly

I just took a closer look at iOutliner, and saw a note saying it was based on the open-code Sproutliner.

Daly