Interesting links:

Research groups:

Pain Imaging Research Group (Department of Human Anatomy & Genetics, University of Oxford)

Pain Research Institute

Magnetic Resonance and Image Analysis Research Centre (MARIARC) - University of Liverpool

Societies:

International Society for Magnetic Resonance in Medicine (ISMRM)

International Association for the Study of Pain (IASP)

American Pain Society

British Pain Society

Research/information resources:

Bandolier - a collection (and meta-analysis) of literally hundreds of research papers relating primarily to the treatment of clinical pain

Pubmed - the ubiquitous research resource

Pubcrawler - the fanatastic web-based search-bot that helps keep me up to date!