Princess Ivy said:
um, sorry to nit pick, but to the best of my knowledge nerilka and coelora have not been released as separate works. they were released as two novella's in one book.
and coelora was originaly intended as part of the proposed series for nemisha's ship (which didn't come about)
also she wrote three stories with with Elizabeth Ann Scarborough, all part of space opera (thats the one about the space pirates which i never managed to read

)
In the UK, The Coelura and Nerilka's Story have only been released in one combined edition, but in the US they've always been separately released.
The Coelura was published years before Nimisha's Ship, so it's the other way around -- Nimisha was written as the start of a new series that occurs in the Coelura universe. It does seem unlikely that Anne will get back to that series, unless inspiration strikes, and her publisher is willing to go for it instead of Pern. But possibly Todd will pick up the series somedays; he's said he has some ideas, and he consulted with his mom on all the ship engineering/design parts of the Nimisha.
Space Opera is a collection of short stories edited by Anne and EA Scarborough. Each of them has one short story in it, and the rest are by other sci-fi authors.
EAS and Anne have also collaborated on the Acorna series, and the Powers That Be series.
The Planet Pirate series is a different series yet again, as Velvet pointed out. The co-authors on that were Jody Lynn Nye and Elizabeth Moon. That series is actually an extension of Anne's series Dinosaur Planet.
I've got a
comprehensive bibliography of all of Anne's books and short stories (well, except perhaps of the last 2-3 releases and I also seem to have left of Space Opera, but that will be fixed soon).