Rank 2010

1. Lockheed Martin Corp. |  Aerospace and Defense | $35,828,421,340.83 |

2. The Boeing Company | Aerospace and Defense | $19,486,294,255.83 |

3. Northrop Grumman Corporation | Aerospace and Defense | $16,797,921,451.22 |

4. General Dynamics Corporation | Defense | $15,249,055,811.75 |

5. Raytheon Company | Aerospace and Defense | $15,245,234,506.52 |

6. United Technologies Corporation | Conglomerate | $7,721,459,648.98 |

7. L-3 Communications Holdings Inc. | Communications and Defense | $7,445,106,575.43 |

8. Oshkosh Truck Corporation | Trucks and Vehicles | $7,243,489,906.25 |

9. SAIC Inc. | Technology and Defense | $6,796,280,361.66 |

10. BAE Systems plc | Aerospace and Defense | $6,561,185,112.84 |

11. Cerberus Capital Management LP | Private Equity | $4,768,901,697.89 |

12. McKesson | Healthcare | $4,601,060,051.58 |

13. Computer Sciences Corporation | IT Services and IT Consulting | $4,372,553,085.04 |

14. URS Corporation | Engineering | $3,947,003,912.81 |

15. Bechtel Group Inc. | Engineering and Construction | $3,939,025,644.12 |

16. Booz Allen Hamilton Inc. | Consulting | $3,748,607,534.52 |

17. KBR Inc. | Engineering, Construction and Private Military Company | $3,625,557,555.82 |

18. Harris Corporation | Communications | $3,301,564,466.11 |

19. Humana Inc. | Health Insurance | $3,248,780,847.62 |

20. Health Net Inc. | Health Insurance | $3,224,143,073.24 |

21. General Electric Company | Conglomerate | $3,134,833,212.85 |

22. ITT Corporation | Conglomerate | $2,814,320,312.00 |

23. Bell Boeing Joint Project | Aerospace and Defense | $2,752,694,557.21 |

24. TriWest Healthcare Alliance Corporation | Health Benefits | $2,721,404,316.04 |

25. Government of Canada | Good Neighbors | $2,678,746,839.33 |

[Source: Wikipedia]

The Top 100 Contractors Report for Fiscal Year 2010 lists contracts totalling $284.7 billion.

In Fiscal Year 2011, the top five departments by dollars obligated were the Department of Defense ($373.6 billion), Department of Energy ($25.1 billion), Health and Human Services ($19.3 billion), Department of Veteran Affairs ($17.4 billion), and NASA ($15.4 billion).