American National Election Studies (ANES)--The ANES series is one of the premier sources for data on voting behavior and political attitudes in the post-WWII United States. Upon registering (which is free), users can download data and SAS/SPSS/Stata program files and documentation for any of the various NES studies. The SDA Archive at UC-Berkeley also allows users to access recent versions of the ANES and extract particular variables from them for those who have specific questions in which they are interested.
Adam Carr's Elections Archive--Excellent link for electoral results around the world, with a special section on Australia. Results are for the most recent elections and are typically broken down into regions or the equivalent electoral constituency.
Comparative Study of Electoral Systems--This site contains data and documentation for a cross-national collection of election studies. The CSES combines microdata on respondents with data at different levels of geography (i.e. data on respondents' electoral districts and on the political institutions of their countries) and focuses on themes such as how macro-level variables such as electoral systems affect political attitudes.
Elections in Western Europe Since 1815--An excellent source of data for historical electoral results by constituency in most Western European countries. Also contains significant information on electoral reform, electoral laws, and political parties in each country. We also have a CD-ROM of this collection of datasets available in the EDC.
European Election Database (EED)--The EED, which is hosted by Norwegian Social Science Data Services, "publishes regional election results according to the Nomenclature of Territorial Units for Statistics (NUTS), level 1 to 3" for a selection of 35 European countries for 1990 onwards. Data are available for parliamentary, presidential, and European Parliament elections.
Lijphart Elections Archive--Holds numerous election results for most democracies. Researchers should note, however, that data is not always great for each country and can differ widely in terms of coverage, detail, and availability.
Parties and Elections in Europe--Parties and Elections in Europe provides election results for national elections and for sub-national elections for selected states, for most of the post-WWII period. The data cover both Western and Central/Eastern Europe.
Political Database of the Americas--Holds numerous election results from most North, Central and South American countries. Researchers should note, however, that data is not always great for each country and can differ widely in terms of coverage and detail.
The Record of American Democracy (ROAD), 1984-1990--The ROAD project, which was headed by Harvard Professor Gary King, collected data on election returns, political behavior, demographics, and boundaries at small levels of geography (e.g. precincts).