DidWhatWhen allows you to store time-stamped text entries which are then browsable in time-based chunks (day, week, month, year).
Common uses include recording minutes in meetings, software changelogs, life histories and micro-blogging. Entries can be marked public or private allowing you to record both personal notes as well as public entries.
For example a software changelog might have only a few public entries marking major releases or events in addition to a detailed log in private entries viewable only by the author.
DidWhatWhen is currently in beta but is missing some key features such as tagging and multiple account support. These are in development.