Convert the Enron email dataset files to a MongoDB.  
Blog post here: http://soloso.blogspot.com/2011/07/getting-enron-mail-database-into.html
Brendan McAdams @rit created a version of the code which utilizes the Python email library to produce a database with more metadata.  You can see the results of his work here: http://mongodb-enron-email.s3-website-us-east-1.amazonaws.com/