JSS Article: Article about the metafor package published in the Journal of Statistical Software.
Other Free/Open-Source Software
Center for Evidence Synthesis in Health: The Center for Evidence Synthesis in Health at Brown University has supported the development of the metafor package in various ways (also by providing some financial support). In addition, the center has developed OpenMeta and OpenMEE, two open-source software packages for conducting meta-analyses that make use of the metafor package as part of the backend.
Meta-Analysis Task View @ CRAN: The meta-analysis task view on CRAN (curated and maintained by Michael Dewey) provides a nice overview of the various R packages related to meta-analysis.