NBER Working Papers
The National Bureau of Economic Research is a private, nonprofit, nonpartisan research organization dedicated to promoting a greater understanding of how the economy works. Nearly 700 NBER Working Papers are published each year, and many subsequently appear in scholarly journals.

BLS Economic Working Papers
Provides complete list (and some full-text) of the Bureau of Labor Statistics Working Papers.

EconPapers
EconPapers provides access to RePEc, the world's largest collection of on-line Economics working papers, journal articles and software.

Economic Working Paper Archive

eScholarship Repository
Research and scholarly output been selected and deposited by the individual University of California units.

European Working Papers
This site provides access to electronic versions of European Working Papers in Business and Economics produced at major European Business Schools

Fed In Print-Working Papers
A comprehensive index to Federal Reserve Economic Research.

IDEAS: Economic and Finance Research
The largest database of working papers available online. Over 550,000 can be browsed or searched and over 450,000 are available in full text.

International Monetary Fund Working Papers 
Searchable by Title, Author or Keyword, the IMF provides full text access to working papers from 1997 to present.

NCEE Working Papers
Provides access to working papers from the National Center for Environmental Economics. Searchable by subject, date, and authors.

Social Science Research Network
The SSRN eLibrary consists of two parts: an Abstract Database containing abstracts on over 182,900 scholarly working papers and forthcoming papers and an Electronic Paper Collection currently containing over 146,600 downloadable full text documents in pdf format.

Working Papers and Technical Reports in Business, Economics and Law
To increase awareness of and access to valuable grey literature in business, economics and law, the Library of Congress provides online access both through its catalog and through these web pages to a growing number of working papers and technical reports in these areas placed online by institutions responsible for creating the reports.