Maybe it's just me, but there some publishers that I don't think you should be allowed to celebrate Novella Month if you're not willing to mention them. One is Mud Luscious, but I'm saving the for later in the month as I hope to have it coincide with something else. One that makes perfect sense to me to mention is Melville House Press. For one thing, they have a whole series of books titled "The Art of the Novella." There's also the "The Contemporary Art of the Novella" series that includes fabulous work like The North of God by Steve Stern.
If I understand properly, as somewhat of a rebel press, they have an affinity for this somewhat of a renegade art form, and I'm very happy that they do. I've picked up and read a fair amount of the titles, both classic and contemporary and never felt slighted once.
They do many other great things over in that little blue house, but when I think of them I usually think of novellas first.