The USIP 'Screaming Hawks' softball team plays in the DC Think Tank Softball League (DCTTSL). Its membership is drawn primarily from staff at the United States Institute of Peace, but also includes friends and family members of colleagues as well as former colleagues.
The DCTTSL is a summer-time co-ed softball league in the Washington, DC area. The teams are mostly from area think tanks but also include representation from a number of government agencies and private firms. The 2010 roster of teams is below:
- Administrative Office of the US Courts - Streetwalkers
- American Enterprise Institute (AEI) - The Brooks Brothers
- Brookings Institution - RBIs
- Catholic Charities
- Cato Institute - Running Dogs
- Center for a New American Security (CNAS)
- Center for American Progress (CAP) - Leftfielders
- Center for Strategic and International Studies - Strategerizers
- Charles G. Koch Foundation - Koch Classical Liberals
- Council on Foreign Relations - New World Order
- Department of Commerce - Dumpers
- Department of State EUR
- Department of State HO - Foggy Bottom Dwellers
- Department of State WHA - WHAqueros
- Drug Enforcement Administration - DEAlers
- Eagle Publishing - Axis of Eagle
- Federal Energy Regulatory Commission (FERC) - FERCules
- German Marshall Fund (GMFUS) - Sauerkrauts
- Hands-on-DC - Renovators
- Heritage Foundation (#1) - Supply Sliders
- Heritage Foundation (#2) - Capitalist Tools
- Institute for Defense Analyses (IDA)
- Institute for Justice (IJ)
- Institute of World Politics (IWP)
- International Republican Institute (IRI)
- Lawyers - Swingers
- Mango Newsletter - The Establishment
- Mathematica - Ballpark Estimates
- National Democratic Institute (NDI) - Little D's
- NDN - Globalization Trotters
- New America Foundation (NAF) - Radical Centerfielders
- NTU/ATR/TF - Dynamic Scorers
- One Economy Corp. - Killer Bees
- Roosevelt Institution - Rough Riders
- Solidarity Center - Molly Maguires
- Urban Institute - Outliers
- U.S. Institute of Peace (USIP) - Screaming Hawks
- U.S. Forest Service
- Washington Scholars Fellowship Program
- Wilderness Society - Sand County Nationals
- Woodrow Wilson Center