Go here -> Xcode -> Other downloads, find the one that contains Snow Leopard in the name.
Download zip from github, unzip, make NO_GETTEXT=YesPlease and then sudo make install NO_GETTEXT=YesPlease
The clang/gcc included in xcode are to old, install it from http://llvm.org/releases/download.html (3.1 works). Symlink everything into the correct positions.
Build from source (google for instructions). Change 10.7 to 10.6 in qtbase/mkspecs/macx-clang/qmake.conf. Configure arguments: -opensource -confirm-license -no-cups -no-dbus -nomake examples -no-sql-odbc -no-sql-sqlite -platform macx-clang
Install using installer
/User/kalle/libexec/git-core/git /Applications/CMake.app/Contents/bin/cmake