TiddlyWiki is a wiki that runs completely inside your web browser, without requiring a server (or even a web connection). It handles micro-content superbly and is great for managing stuff like your personal to-do lists.
Chandler Project is an open source, standards-based personal information manager (PIM) built around small group collaboration and a core set of information management workflows modelled on Inbox usage patterns and David Allen's GTD methodology.
Y. Cai, X. Dong, A. Halevy, J. Liu, and J. Madhavan. Proceedings of the 2005 ACM SIGMOD conference on Management of data, page 921--923. New York, NY, USA, ACM Press, (2005)