DOAJ: business and management collection
Open access to 579,107 e-prints in Physics, Mathematics, Computer Science, Quantitative Biology, Quantitative Finance and Statistics:  arXiv.org
  An open-access journal in economic theory: Theoretical Economics

you can read the full text of open access dissertations and theses free of charge:  PQDT open

 Research Papers in Economics:  Repec

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