Since there have threads about other squashes, I thought I'd mention my experience with a turban squash.
I bought a fairly large one several weeks ago, as much intrigued by its decorative potential as flavor. Today I cut it open, carefully separating the narrower top from the base. It's a pretty hard squash, requiring repeated stabbing cuts with a narrow, serrated paring knife. After scooping out the seeds, I roasted it in a 350 oven with the cap on. I also toasted the seeds till they started to pop.
The cap got soft before the base, so I took that out, and scooped out the flesh. Then scooped out flesh from the base as it got soft. Total cooking time about a hour.
The flesh was pretty soft and smooth, but I went ahead and ran it through the food mill. About half was seasoned with cream, maple syrup, salt, dried ginger, and a bit of chipotle sauce. The rest is in the fridge for later use.
In contrast to other squashes that I've worked with, the shell of this one remained hard. So I've cleaned out all the flesh on the inside, and am letting it dry. Hopefully it will last to Thanksgiving so I can use it as a center piece. The base is intact, so it is tempting to use it as a serving bowl, but I'll probably use an insert bowl.