These are a couple of good, comprehensive websites with information about Gestalt therapy.
Background information on Gestalt Therapy (www.gestalt.org/yontef.htm)
Theories and ideas in Gestalt Therapy (www.afn.org/~gestalt/about.htm)
EGI is a registered educational charity based in Edinburgh that offers personal and professional development in relational, embodied Gestalt psychotherapy.
GPTI is a national coordinating and accrediting body. It does not itself offer training programmes in Gestalt. These are offered via the independent training organisations and the trainers associated with them. GPTI also accredits Gestalt psychotherapy trainers and supervisors.
UKCP holds the national register of psychotherapists and GPTI is a member of this body.
BACP is a professional body representing counselling and psychotherapy.