If you read one article on Yemen today, it should be this one by Charles Schmitz up at Foreign Policy. 

In concise prose, Schmitz walks us through the summer and early fall in Yemen, detailing how the country has reached such a precarious point.

The article gives an excellently sober overview of what has happened in Yemen, I highly recommend it.  (The only thing I disagree with is the title and subtitle, and I don't think those were the author's.)

Schmitz, as so many Yemen watchers, is pessimistic.

His conclusion:

"The only real hope for Yemen now is another unexpected political surprise that will lead to a transitional government and legitimate elections. Given Saleh's evident advantage in a now deeply fractured and divided country, that is a thin hope indeed."