The definition of "Bias towards Obama" is straightforward:
(Pro Obama% / Anti Obama%) / (Pro McCain% / Anti McCain%)
A value of 1 shows no bias, values significantly greater than 1 show a bias towards Obama, and values less than 1 show a pro-McCain bias. For the VP Debate, substitute Biden and Palin for Obama and McCain. The CBS "anti" numbers were not given in the data, but were said to be "similar to overall", so I put in the overall numbers.
Conclusion: other then Fox, the media was seriously "in the tank" for Obama. Which is why the Saturday Night Live spoofs ring so true.