Once a week I sit down with my notebook and jot down 10-20 ideas. The ideas can be anything from business ideas to ideas on being more efficient throughout the day, whatever comes to mind when I start basically.
One of the brief ideas I had a few weeks ago was a group email service. A service for club sport groups, groups of friends, planning a trip, SXSW RSVP lists, etc. Basically an easy way to keep everyone up to date around some common thread.