Fedora-Jam-x86_64-20121218.iso roughly corresponds to the Fedora 18 test compose 3, so is still 'pre-release', please use with care.
sha256sum:
a3f3b45be239b7b5409ee5b2a18b5ffeb23c122c3e0ff8183e3128d3b03d1447  Fedora-Jam-x86_64-20121218.iso