Since August, 2006, there is a promising new package called biblatex. It enables you to have the citation style you need with little effort. Although it is still regarded as a beta version for test cases only, it works like a charm with my documents—I have been using it since the end of 2006.
You can also have a look at my
A historian's biblatex styles.
biblatex has another way of using BibTeX than other packages, as emerges from the self-description in the documentation:
This package provides advanced bibliographic facilities for use with
LaTeX in conjunction with BibTeX. The package is a complete reimplementation
of the bibliographic facilities provided by LaTeX. It redesigns the way in which
LaTeX interacts with BibTeX at a fairly fundamental level. With biblatex, BibTeX
is only used to sort the bibliography and to generate labels. Instead of being
implemented in bst files, the formatting of the bibliography is entirely controlled
by LaTeX macros, hence the name biblatex. Good working knowledge in LaTeX
should be sufficient to design new bibliography and citation styles. There is no
need to learn BibTeX’s postfix stack language. This package also supports
subdivided bibliographies, multiple bibliographies within one document,
and separate lists of bibliographic shorthands. Bibliographies may be subdivided
into parts and/or segmented by topics. Just like the bibliography styles, all citation
commands may be freely defined. The package is completely localized and
can interface with the babel package.
biblatex documentation (Version 0.8), p. 1–2