In the UK there is the Energy Storage Research Network (http://www.esrn.co.uk) which covers PCM as well. I myself are interested in the design of thermal energy storage systems but not so much in the chemistry itself.
Several companies that develop and sell PCM or related products are members of this association.
In addition, the Quality Association provides testing specification for the characterisation of PCM (e.g. determination of storage capacity via calorimetry / thermal cycling stability / measurement of heat conductivity).
Please contact me if you have further questions concerning the work of the Quality Association.
There is a conference on thermal energy storage coming up where there usually are discussions on PCMs: http://greenstock2015.csp.escience.cn/dct/page/1