The Standing Liturgical Commission of The Episcopal Church is developing resources for blessing same-sex relationships.
As explained here:
The 2009 General Convention of The Episcopal Church acknowledged the changing circumstances in the United States and in other nations, as legislation authorizing or forbidding marriage, civil unions or domestic partnerships for gay and lesbian persons is passed in various civil jurisdictions that call forth a renewed pastoral response from this Church. In light of these circumstances, the General Convention directed the Standing Commission on Liturgy and Music to collect and develop theological and liturgical resources for blessing same-gender relationships. At the same time, we were asked to invite theological reflection from throughout the Anglican communion…
The Commission has recently published two documents as PDF files:
These materials are discussed in an article at the Living Church SCLM Lists Principles for Same-sex Blessings.