I love John Varley's Titan trilogy (Titan, Wizard, Demon). It's so much fun, and so darn cinematic too. I'd love to see them done as a movie someday. I bet in a few years the special effects will be up to it.
But I've never been able to cast Cirocco Jones in my head. But just now I realized Claudia Black would be the perfect match for that role. She has the perfect strong features and rough beauty for the role, and she's a fine actress too. The other roles aren't so hard to cast, but Cirocco is critical. I guess Uma Thurman would make a good Cirocco too, now that I think of it. Just as long as they don't fuck up the casting like the did with John Constantine.