These graphs plot my task completion counts by week, month, and year.
I record my task list in Remember the Milk and this system periodically queries my account for updated progress.
Note that these are raw counts and caution should be applied when interpreting this data as anything approximating effort expended, time spent, etc. A single task plotted here can encompass a variety of magnitudes, from something as simple as taking a vitamin each day to something as complex as implementing an entire subsystem for a product under construction.