I keep a quotes file. I’ve kept a quotes file since I was in college, although my original one was in a notebook and got lost in the fire, so the one I have currently only dates back a few years. In it, I note things that strike me as either funny or profound. Some of them are from famous people, but many of them are just things that see in the course of reading Livejournal or Usenet or mailing lists or whatever i happen to be perusing.
Sometimes, I go through it to see what jumps out at me, and then I ponder that for a while. It’s a good way of focusing my mind, and sometimes I’ll find that something hits me with a different or deeper meaning than it did when I first selected it.