European Elections Database (EED)
http://www.nsd.uib.no/european_election_database/
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.
Eurostat
http://epp.eurostat.ec.europa.eu/portal/page/portal/eurostat/home/
Eurostat is the statistical office of the European Union. Eurostat collects statistical information from the member states of the EU, and its databases constitute a very comprehensive source for economic and social data for EU members at both the national and sub-national/regional level. Some of its databases also include data for countries in Central and Eastern Europe. Much of their data are accessible on-line here. The EDC also has a DVD database with more extensive time-series coverage. The DVD database has an on-line interface. Please note that none of the interfaces is entirely user-friendly.
OECD (Organization for Economic Cooperation and Development) Fiscal Decentralisation Database
http://www.oecd.org/tax/federalism/oecdfiscaldecentralisationdatabase.htm
"The OECD fiscal decentralisation database provides comparative information on the following indicators analysed by level of government sector, [Federal or Central (including Social Security), State/regions and Local] for OECD member countries between 1965 and 2011." The data are national-level data that provide estimates of total government spending various levels - central, state/region, and local.
OECD (Organization for Economic Cooperation and Development) iLibrary
http://www.oecd-ilibrary.org/
The OECD iLibrary is an online interface that provides full-text access to OECD studies, periodicals, and dozens of statistical databases via OECD.Stat. The topical range of the iLibrary is considerable and covers areas such as agricultural policies, environmental indicators, social expenditures, labour markets, national accounts, foreign trade and FDI, and various industry-level data. The various OECD.Stat databases include collections for regional data and measures of fiscal decentralization.
Party Government Data Set (PGDS)
http://www.fsw.vu.nl/en/departments/political-science/staff/woldendorp/party-government-data-set/index.asp
The Party Government Data Set, hosted by J.J Woldendorp at the University of Amsterdam, "covers 39 parliamentary democracies from 1945, or the year these countries became a parliamentary democracy (again), through 2008." The geographic focus is on countries in Western and Eastern Europe. The data cover topics such as reason for government termination, ideological orientation of government, names of parties in government, and size of governing coaliation (e.g. minority governments).
Quality of Government (QOG) Institute
http://www.qog.pol.gu.se/
The QOG Institute is hosted by members of the Department of Political Science at Göteborg University in Sweden and is devoted to "the causes, consequences and nature of 'good governance.'" The Institute has created four collections of data on governance: a broad collection of governance indicators that is global in coverage; a more narrow collection that focuses on social policy in wealthier countries; data from expert surveys on politicization and professionalization of public administration in individual countries, and a new data collection on perceptions of corruption in individual regions within EU members. The data are compiled from multiple sources, including the Polity IV Project, the Cingarelli-Richards Human Rights Data, Transparency International, Freedom House, various international organizations, and datasets produced by various academics. The QoG data are available in SPSS, Stata, and comma-delimited (.csv) formats. The Institute has also compiled a very nice collection of links to other governance-themed data (some free, some fee-based) compiled by various sources.
Regional Authority Index (RAI)
http://www.falw.vu/~mlg/rai.html
The Regional Authority Index "measures the formal authority of intermediate or regional general-purpose government [and] tracks regional authority on an annual basis from 1950 to 2010 ... [it] is a measure of the authority of regional governments on an annual basis across eight dimensions: institutional depth, policy scope, fiscal autonomy, representation, law making, executive control, fiscal control, constitutional reform." Data are coded at both the national and regional levels. The data are also available via UNC-Chapel Hill.