A link (or at least a page reference), from the bibliography to the citing command, is often useful in large documents.
Two packages support this requirement, backref and
citeref. Backref is part of the
hyperref bundle, and supports hyperlinks back to the citing
command. Citeref is the older, and seems to rely on rather
simpler (and therefore possibly more stable) code. Neither collapses
lists of pages ("5, 6, 7" comes out as such, rather than as
"5-7"), but neither package repeats the reference to a page that
holds multiple citations. (The failure to collapse lists is of course
forgiveable in the case of the hyperref-related
backref, since the concept of multiple hyperlinks from the
same anchor is less than appealing.)
This question on the Web: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=backref