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Social Explorer is the best interface into Census data. The Census breaks out data by Congressional District. Just select the data source (e.g. Census 2010) and choose "congressional district" for your geography.
More information in Catalyst...
Published annually by the Council of State Governments, this compendium is the definitive resource for what's happening year-by-year, at a glance but in rich detail all the same, in state legislatures. The library has 1937-current, with the most recent issue in Reference. Also now available online.