James Pfeiffer: 3.8.  Really *short*, but useful.  His talk was awesome.
The code is somewhat silly.

Andrew Barr: 4.0.  great work.  very well researched.  I really like this.
It is even comparatively well proof read.  Many good examples.
Focused on a clear topic nicely.

Alyson Deines: 

Chris Swierczewski:

Joanna Gaski: