The Bureau of Justice Statistics (BJS) published the Federal Justice Statistics – 2008 statistical tables.  They are  now available in PDF or as a spreadsheet.

[It] describes criminal case processing in the federal justice system, including arrest and booking through sentencing and corrections. These statistical tables present the number of suspects arrested and booked by the U.S. Marshals Services, suspects in matters investigated and prosecuted by U.S. attorneys, defendants adjudicated and sentenced in U.S. district court, and characteristics of federal prisoners and offenders under federal supervision.