Note:  This list was updated on June 3, 2010.

Tweet aggregator:

• Tweeting Economist: @TweetEcon
  A Twitterbot that collects economics related tweets from many different sources and retweets the most relevant messages.

Economists:

• Tyler Cowen: @tylercowen
• Brad DeLong: @delong
• Patrick Emerson: @OregonEconomics
• Richard Florida: @Richard_Florida
• Eric Fruits: @ericfruits
• Paul Krugman: @nytimeskrugman
• Wayne Marr: @WayneMarr
• Nouriel Roubini: @Nouriel
• John Rutledge: @johnrutledge
• Arnav Sheth @arnavsheth
• Mark Thoma: @MarkThoma
• Jamie Woods: @woodsjam

Think tanks:

• Brookings: @BrookingsEcon
• Cato Institute: @CatoInstitute
• Center on Budget and Policy Priorities: @CenterOnBudget
• The Hayek Center: @FriedrichHayek
• Heritage Foundation: @Heritage
• Hoover Institution: @HooverInst
• Ludwig von Mises Institute: @mises
• Milken Institute: @MilkenInstitute
• National Center for Policy Analysis (NCPA): @NCPA
• National Taxpayers Union: @NTU
• Tax Policy Center: @TaxPolicyCenter

Some news sources focusing on economics:

• Financial Times: @financialtimes
• Financial Times – U.S. Economy: @ftuseconomy
• Financial Times – Economists Forum: @economistsforum
• Economics Webpartner: @economicsnews
• The Economist: @theeconomist
• Wall Street Journal: @WSJ_Econ
• Wall Street Journal – Economics: @WSJ_Econ

Please send a Twitter DM to @ericfruits if you have any more to add.