Aswath Damodaran

 is a Professor of Finance and David Margolis Teaching Fellow at the Stern School of Business at New York University.

Online data sets
Corporate finance, valuation, and portfolio management data which is available for download. Caveats and rules for data usage is here.
 * Useful Data Sets

Academic papers
Most of these papers are applied papers, relating to estimation issues commonly faced in corporate finance, portfolio managment and valuation.
 * Papers and Research

Books

 * Books

Spreadsheets
These corporate finance and valuation spreadsheets are free to download and modify.
 * Spreadsheet programs