The following WSJ page has the amount of exposure different people and groups had to Madoff. The amounts are astounding, but even more surprising is the amount of exposure some of these firms had to a single investor.
Bank Medici: The bank had two funds with $2.1 billion (1.5 billion euros) invested with Madoff. Bank Medici is 25% owned by Unicredit SpA and 75% owned by chairwoman Sonja Kohn. Hedge funds run by the bank had almost all their money invested with Madoff...
http://s.wsj.net/public/resources/documents/st_madoff_victims_20081215.html
We had also wondered what happened to Madoff's co workers and the rest of his money last week in class. Here is an article that explains part of it anyway. Madoff has talked to his prison "roommate" about it, telling him that he thinks his coworker, Frank DiPascali, has used the knowledge knowing the lcoation of $9 billion as leverage to push for a plea bargain with the law.
http://www.nypost.com/p/news/local/madoff_HD9ShMJK26jjNYTFSO7LpJ
And here is an article about other people that may have known or benefited from the Madoff scheme
http://www.cbsnews.com/stories/2010/06/03/business/main6544040.shtml