I have started keeping a personal journal. I wrote backdated entries for January 1 - 3, since I wanted to start it on the first day of the year, and began keeping it in earnest on January 4. Some of what I used to write on here will probably end up there instead.
I suspect this journal will be very useful to me, since it remembers my life much better than I do. From now on, I'll be able to tell people exactly what date various events happened on. For major life events and historical events, I'll be able to go back and see how I reacted to it at the time.
I make sure to highlight important parts so I can skim through and locate stuff later on.