Crossed Genres is accepting submissions for their anthology Long Hidden: Speculative Fiction From The Margins of History! Click through for the guidelines, and submit by July 31, 2013! The anthology is in the hands of Daniel Josè Older and Rose Fox.
While not specifically steampunk, they do accept alternate-history type spec fic, which can also include steampunk. If you're not sure whether or not your story will work, you can email them (firstname.lastname@example.org) to find out! PLEASE make sure you address it "Dear Long Hidden editors," "Dear Mr. Older and Mx. Fox" OR "Dear Rose and Daniel". This makes sure you're addressing both editors; the editorial team is working as a team, and you should acknowledge them as such.