After several years of study, the Episcopal Church has released a draft of what same-sex marriage rites would look like. An important caveat: these are just drafts, and it will likely be years before any final liturgy is approved for official use across the church.
Episcopalians in states that allow same-sex civil marriage (Massachusetts, Connecticut, Maryland and others) already have the option to bless same-sex marriages but there is no formal churchwide liturgy. Same-sex commitment ceremonies are permitted elsewhere in the church at the discretion of the local bishop.