The 'Blender's VSE' Blog has compiled a collection of awesome Sequencer Python scripts.
Blender's VSE writes:
The Blender VSE or Sequencer is a very capable video editor. But it lacks some key features of other NLEs (Non Linear Editors). Fortunately some dedicated users became developers in their own right and crafted some really useful python scripts. Now the VSE does not have a lot of code exposed to manipulate, but what is there is quite handy.