I'm finding LiveJournal to be really useful for keeping track of my personal info. I've got two logs going right now: one is weight-loss log where I've tracking my current goal, my meals, my daily weight reading, and my physical activities. The other is a log I'm keeping for work where I'm writing down all of my activities so I can prepare useful status reports at the end of the week. I'm already doing a lot of posting to LJ, so keeping these up to date doesn't take me out of my writing context.
Several attributes make LJ a useful platform for this activity:
I can post private entries that only I can access, but I can get to this data from any computer with a browser.
I can use the backdating feature to make the posting date and time of the entry to the end of the week, so they will always show up at the top of my "Recent Entries" view.
I can drag the "edit post" button from the entry comments page to my Mozilla Firebox toolbar, giving me one-button access to a form where I can edit the log.