A very sad day and a scary day for any one with a familiarity with the complexity of Pakistan's politics. Note that Musharraf's approval is in the single digits (that would be under 9%). Bhutto was over 60%.
I recommend three brief articles
Benazir Bhutto's own statement - a blog entry - on September 1, 2007, entitled Why I'm Returning to Pakistan.
Steve Coll writing in The New Yorker a short piece entitled Miscalculations. (those would be Musharraf's miscalculations abetted by the Bush Administration). This piece gives a good overview of the crises facing Pakistan as of November 19th, 2007.
Finally Michael Hirsch, a Newsweek reporter writes Dancing with the Dictator - How Bush's tight relationship with Pakistan's Musharraf has compromised the war on terror.