For emerge-like script look at cygport, which was ITP'ed last week in cygwin-apps.
Holy hippo, when at last will I stop reinventing the wheel ?! It just seems like everytime I have some kind of idea and seriously start to work on it, someone has the sneaky idea to release an equivalent project, thus blowing my motivation to bits. Last time for a project of mine, I felt like I had to dev' (and did) a php db abstraction layer+api which autogenerates stuff, just to discover rails does just fit in for the need (though I don't know ruby, and RoR seems to be lacking in terms of docs and community). BTW, while we're on success stories, I managed to make lighttpd/ruby/rails/mysql work quite nicely under cygwin, which was close to a RPITA for some reason. Concerning cygport, it seems like a great package, though from what I read I could not grasp its exact goal. Mine was to give packages major configurability through use flags and live compilation, and to take inspiration from gentoo customizable/scriptable installation schema, effectively making it some sort of alternate distro (though mainly for personal use only). I might just continue to dev' it for learning purpose, and if someday I feel like it's relevant enough, publish it on the www (which I highly suspect will, as always, never happen). Lloeki