Just wanted to give a quick update on my unripe pumpkin. Two weeks ago, I had to clean up my dying squash vines and harvested all remaining fruit. This brave little guy (pictured above) wasn't yet ripe. So I placed him in a sunny, warm location and look at his progress:
It's my hunch that this will work with winter squash in general, so long as the fruit has reached a certain level of development (pretty much full size and just waiting to ripen) before it's separated from the vine.
All in all, my little volunteer pumpkin plant produced well for me this year. And although they are not ideal eating pumpkins--they are a variety sold for carving as Halloween decor--I shall toast the seeds and cook the rest down into puree to keep in freezer for use this winter.