Your best place to start is the GAO. Go to their website www.gao.gov and just start browsing around, you'll be pissed at what you find, but it is chock full of good info, recommendations and reports.
For some specifics...
Government Accountability Office, Improper Payments: Progress Made but Challenges Remain in Estimating and Reducing Improper Payments, GAO-09-628T, April 22, 2009, at
http://www.gao.gov/new.items/d09628t.pdfStephen Slivinski, “The Corporate Welfare State: How the Federal Government Subsidizes U.S. Businesses,” Cato Institute, May 14, 2007, at
http://www.cato.org/pub_display.php?pub_id=8230Office of Management and Budget, Budget of the U.S. Government, FY 2010: Analytic Perspectives (Supplemental Materials), May 2009, at
http://www.whitehouse.gov/omb/budget/fy2010/assets/homeland.pdfSubcommittee Oversight Efforts Identify $1.1 Trillion in Waste or Questionable Spending, October 19, 2006, at
http://coburn.senate.gov/oversight/?FuseAction=OversightAction.Home&ContentRecord_id=611f1f4c-802a-23ad-475d-223d6490f308Congressional Budget Office, “Budget Options, Volume 1: Health Care,” December 2008, at
http://www.cbo.gov/ftpdocs/99xx/doc9925/12-18-HealthOptions“Budget Options, Volume 2,” August 2009, at
http://www.cbo.gov/ftpdocs/102xx/doc10294/08-06-BudgetOptions.pdfCommittee on Governmental Affairs, U.S. Senate, “Government at the Brink,” Vols. I and II, June 2001; U.S. General Accounting Office, “Managing for Results: Using the Results Act to Address Mission Fragmentation and Program Overlap,”, at
http://www.gao.gov/archive1997/ai97146.pdf“U.S. Will Pay $2.6 Million to Train Chinese Prostitutes to Drink Responsibly on the Job,” CNS News, May 12, 2009, at
http://www.cnsnews.com/public/content/article.aspx?RsrcID=47976Government Accountability Office, Government-wide Purchase Cards: Actions Needed to Strengthen Internal Controls to Reduce Fraudulent, Improper, and Abusive Purchases, GAO-08-333, March 2008, at
http://www.gao.gov/new.items/d08333.pdfMarc Stewart, “Federal Gov’t Questions TVA Spending,” WBIR.com, February 27, 2009, at
http://www.wbir.com/news/local/story.aspx?storyid=79461Dan Eggen, “Federal Credit Cards Misused,” The Washington Post, April 9, 2008, at
http://www.washingtonpost.com/wp-dyn/content/article/2008/04/08/AR2008040802718.htmlRobert Brodsky, “Report Paints Agencies as Deadbeat Travel Card Holders,” Government Executive, May 28, 2009, at
http://www.govexec.com/story_page.cfm?articleid=42837&dcn=todaysnewsLaura Strickler, “SEC Spends Millions to Reorganize Desks,” CBS News, April 8, 2009, at
http://www.cbsnews.com/stories/2009/04/07/cbsnews_investigates/main4927475.shtmlTony Capaccio, “Pentagon Paid $998,798 to Ship Two 19-Cent Washers,” Bloomberg, August 16, 2009, at
http://www.bloomberg.com/apps/news?pid=20601070&sid=aY5OQ5xv9HR8Ted Covey et al., “Agriculture Income and Finance Outlook,” U.S. Department of Agriculture, Economic Research Service, November 2006, pp. 40 and 48.
Carrie Johnson, “Medical Fraud a Growing Problem,” The Washington Post, June 13, 2008, at
http://www.washingtonpost.com/wp-dyn/content/article/2008/06/12/AR2008061203915.htmlDana Hedgpeth, “GAO Blasts Weapons Budget,” The Washington Post, April 1, 2008, at
http://www.washingtonpost.com/wp-dyn/content/article/2008/03/31/AR2008033102789.htmlChristopher Conkey, “Federal Workers Accused of Abusing Business Class,” The Wall Street Journal, October 3, 2007, at
http://online.wsj.com/article/SB119136054325946827.htmlBrad Heath, “Gov’t Losses Big in Home Market,” USA Today, May 15, 2009, at
http://www.usatoday.com/money/economy/housing/2009-05-14-govtown_N.htmDana Hedgpeth, “$13 Billion in Iraq Aid Wasted or Stolen, Ex-Investigator Says,” The Washington Post, September 23, 2008, at
http://www.washingtonpost.com/wp-dyn/content/article/2008/09/22/AR2008092202053.htmlDan Friedman, “Report: Defense Department Cannot Fully Account for $7.8B Spent in Iraq,” CongressDaily, May 22, 2008, at
http://www.govexec.com/dailyfed/0508/052208cdpm2.htmAssociated Press, “Katrina Fraud Could Top $2 Billion,” December 25, 2006, at
http://www.msnbc.msn.com/id/15587326“FEMA Funds Spent on Divorce, Sex Change,” June 14, 2006, at
http://cbs4denver.com/national/FEMA.Divorce.Sex.2.268906.htmlGovernment Accountability Office, Expedited Assistance for Victims of Hurricanes Katrina and Rita: FEMA’s Control Weaknesses Exposed the Government to Significant Fraud and Abuse, GAO-06-403T, February 13, 2006, p. 11, at
http://www.gao.gov/new.items/d06403t.pdfGovernment Accountability Office, DOD Travel Cards: Control Weaknesses Led to Millions of Dollars in Unused Airline Tickets, GAO-03-398, March 2004, at
http://www.gao.gov/new.items/d04398.pdfGovernment Accountability Office, Travel Cards: Air Force Management Focus Has Reduced Delinquencies, but Improvements in Controls Are Needed, GAO-03-298, December 20, 2002, p. 4, at
http://www.gao.gov/new.items/d03298.pdfTravel Cards: Control Weaknesses Leave Navy Vulnerable to Fraud and Abuse, GAO-03-148T, October 8, 2002, p. 8, at
http://www.gao.gov/new.items/d03148t.pdfDepartment of Heath and Human Services, Office of the Inspector General, “Compendium of Unimplemented Office of Inspector General Recommendations,” May 2009, at
http://oig.hhs.gov/publications/docs/compendium/compendium2009.pdfChristopher Lee, “Official Portraits Draw Skeptical Gaze,” The Washington Post, October 21, 2008, at
http://www.washingtonpost.com/wp-dyn/content/article/2008/10/20/AR2008102003627.htmlDan Morgan, Gilbert Gaul, and Sarah Cohen, “Farm Program Pays $1.3 Billion to People Who Don’t Farm,” The Washington Post, July 2, 2006, at
http://www.washingtonpost.com/wp-dyn/content/article/2006/07/01/AR2006070100962.htmlGovernment Accountability Office, Purchase Cards: Control Weaknesses Leave DHS Highly Vulnerable to Fraudulent, Improper, and Abusive Activity, GAO-06-1117, September 2006, at
http://www.gao.gov/new.items/d061117.pdfJonathan Rockoff, “NIH Paying $1.3 Million Monthly for Unused Lab,” Baltimore Sun, December 2, 2007.
David Stout, “Medicare Error Sends $50 Million in Refunds to Recipients,” The New York Times, August 24, 2006, at
http://www.nytimes.com/2006/08/24/washington/24medicare.htmlGriff Witte and Spencer S. Hsu, “Homeland Security Contracts Abused,” The Washington Post, July 27, 2006, at
http://www.washingtonpost.com/wp-dyn/content/article/2006/07/26/AR2006072601683.html