paul wheaton
Almost Self-Reliant
This video shows Helen Atthowe talking about penny cress. If you leave it alone (read: don't pull it out or smother it like you might do with other weeds) it will reseed, grow in the early spring and then go dormant - providing your garden plants with a helpful mulch that does not compete.
http://www.youtube.com/watch?v=1_fBY5UG-Q4
http://www.youtube.com/watch?v=1_fBY5UG-Q4