Language Log linked to an OED post on that dictionary's "release notes" for updated entries on words to do with gender and sexuality. The post title says "formal language" but the discussion includes "trans*" and "cis," which don't feel formal to me, as well as "heterosexual" and the changing meanings of "bisexual" over time and in different contexts.

The author notes that the editors made extensive use of the Digital Transgender Archive. The earliest citations the OED could find for agender and cisgender were on Usenet. (On the other hand, the earliest usage they found for "transgendered" was from the TV magazine section of the Des Moines Sunday Register.