I've never heard of them. They've got some skilled designers working with them--those covers look every bit as slick as the "urban fiction" covers Big Six houses are putting out.
They also seem to have a very, very focused list, which is interesting. Not only is it all of the "gangsta soap opera" sub-subgenre of the urban fiction subgenre, but all the books seem to focus around empowered female protagonists finding self-actualization through criminal activities. I kind of love books like that (and TV shows and movies--Joan Collins's Alexis was always my favorite on Dynasty).
So, do you have a manuscript to send them that is in tune with what they're publishing? Though I have to say that if I did, I still might send to Atria or Strebor or Dafna first, because my guess is that those Big Six urban fiction imprints pay better.
Still, I'm impressed by the design savvy at Melodrama and its level of focus. Too many small publishers try to be all things to all readers; representing a still under-resourced market niche is a great strategy.
I would encourage them to try Atria and Strebor and Dafna first, just because of the potentially bigger paycheck--I am pretty sure that all of those imprints accept unagented submissions even where the larger publishers of which they're a part don't--but if they can't find a place for that manuscript there, these Melodrama folks look good to me.