Shapely Windows installers
Christoph Gohlke has 5 different 32 and 64 bit Windows installers for the latest version of Shapely (1.2.16) and scores of other CPython extension package installers (GDAL, Numpy, etc) at http://www.lfd.uci.edu/%7Egohlke/pythonlibs/#shapely (Via GIS StackExchange).
Update (2012-11-01): Following a suggestion by Howard Butler, Christoph has added Rtree to the list.