ConnectedText - ConnectedText is a powerful but simple information management system.
TheBrain - TheBrain: The Ultimate Digital Memory
TiddlyWiki - a non-linear personal web notebook
AllMyNotes Organizer - AllMyNotes Organizer is a multi-functional hierarchical information manager for Windows.
wikidPad - wikidPad is an application for storing thoughts, ideas, todo lists, contacts, or anything else that user can think of to write down.
Diigo - Diigo is a powerful research tool and a knowledge-sharing community