Sign ups haven't started yet; the tag set is built up from the ships people have nominated because they're considering requesting or offering them, and we're now in the final stages of making sure it's ready.

Once sign ups do start (in about three days), all requests will be visible on AO3 here. Any letters people write will be linked from there; given the relatively small scale of the exchange and the fact that requests are visible throughout, we haven't seen the need for a separate letters post.