An author index can be generated from BibTeX by using the authorindex package, available on CTAN where there are details of limitations, including some bibliographic styles that require patching to use with authorindex. It is included in TeXlive. texdoc authorindex will give details of options.
authorindex uses a provided perl script to run against .aux files to generate the author index. The index can take several forms, for example a list of authors referenced or a more detailed list of authors and pages where their works are cited (using \aicite rather than the more usual \cite is one way this can be done).
This trivial example shows the package in use but without any of its formatting options:
\documentclass{article}
\usepackage{blindtext}
\usepackage{authorindex}
\bibliographystyle{apalike}
\begin{document}
Found in \aicite{diller97} and \aicite{goossens99}
\blindtext[6]
Found in \aicite{goossens99}
\blindtext[10]
In \aicite{syropoulos03} but not \cite{patashnik88}
\blindtext[3]
Finally, \aicite{voss10}.
\bibliography{TeX}
\printauthorindex
\end{document}
This generates a 5-page pdf file and the end of the final page is:

biblatex. – lockstep Jul 28 '11 at 15:07