One useful entry into this literature is
@misc{cousins08, author = {Cousins, R D}, title = {Annotated bibliography of some papers on combining significances or $p$--values}, year = {2008}, note = {arXiv:0705.2209} }
an annotated bibliography by R D Cousins which considers most of the well-known methods for combining $p$-values and which is freely available from arXiv and discusses most of the best known methods.