Shapely 1.2 source distribution and Windows installers for win32 and amd64 have been uploaded to http://pypi.python.org/pypi/Shapely and http://gispython.org/dist/. See the wiki for links to all the distributions.
To install and try it out (in a virtualenv):
I always like to remind my readers that Shapely is a spin-off from a publicly-funded project. Major portions of this work were supported by a grant from the U.S. National Endowment for the Humanities (http://www.neh.gov). Factoring more widely useful packages out of our specialized ancient world studies application is part of our sustainability strategy. It pays off: most of the hard work toward 1.2 was done independently by Aron Bierbaum. I'm very pleased with the public/private interest collaboration we've got going on.
Share and enjoy.