It is advisable to try the pre-compiled package for your distribution before you try to make GNOME Power Manager from source.
You can check out the latest GNOME Power Manager code using GIT. You can use the gitweb interface too.
git clone git://git.gnome.org/gnome-power-manager
To compile and make, use the following procedure:
cd gnome-power-manager ./autogen.sh --prefix=/home/hughsie/root --enable-applets --with-gconf-source=xml::/home/hughsie/.gconf make make install