Outspline - Extensible outliner and personal time organizer to manage todo lists, schedule tasks, remind events.
Dynalist - Dynalist is a web app that lets you break down and organize your thoughts in the format of lists.
EditiX - EditiX is a quality Open Source XML Editor and XSLT Editor for Windows, Mac OS X and Linux. Test for Free with our 30-day Trial !
Workflowy - A better way to organize your mind.
Firstobject XML Editor - Firstobject's free XML editor for Windows is called foxe.
OmniOutliner - OmniOutliner is a writing app for collecting information, outlining ideas, adding structure to any sort of writing.