The International Monetary Fund (IMF) and the World Bank are two of the main sources of financial data at the country level.
The International Monetary Fund (IMF) provides access to numerous reports as .pdf downloads and tables as .csv or Excel downloads at http://www.imf.org/external/data.htm . This page includes links to downloadable data from the IMF's World Economic Outlook. Some of the IMF data has to be purchased, although five day trials are offered for the for purchase data bases.
The World Bank provides financial data in its WDI data base.
United Nations -- Data on the financial indicators related to the Millennium Development Goals is available at http://unstats.un.org/unsd/mi/mi_goals.asp .