Soon after GNOME 2.18.1 release, here is compatible gswitchit-plugins release.

The plugins add several missing not too HIGgish bits to the standard gnome keyboard indicator applet. The most wanted, of course, being the flags.

Feel free to download from either sf.net:

http://prdownloads.sourceforge.net/gswitchit/gswitchit_plugins-0.7.tar.gz?download

or GNOME Subversion (using the tag v_0_7).