Once you have written a document with labels, references and
citations, it can be nice to read it like a hypertext document.
RefTeX has support for that:
reftex-view-crossref (bound to C-c
&), reftex-mouse-view-crossref (bound to
S-mouse-2), and reftex-search-document. A
somewhat fancier interface with mouse highlighting is provided
(among other things) by Peter S. Galbraith's bib-cite.el. There is some overlap in the
functionalities of Bib-cite and RefTeX. Bib-cite.el comes
bundled with AUCTeX.
Bib-cite version 3.06 and later can be configured so that
bib-cite's mouse functions use RefTeX for displaying
references and citations. This can be useful in particular when
working with the LaTeX xr package or with an
explicit thebibliography environment (rather than
BibTeX). Bib-cite cannot handle those, but RefTeX does. To
make use of this feature, try
(setq bib-cite-use-reftex-view-crossref t)