The Clicky GUI comes with Click, in the apps/clicky directory. This silent screencast shows what it's about (click "Go" to begin).
Clicky can show Click configurations as text (with syntax highlighting) or diagrams, and can read and write handlers in live configurations. It can also generate output diagrams in PDF format.
To build the Clicky GUI you will need recent packages for autoconf, automake, and GTK+. On Ubuntu "libgtk2.0-dev" should suffice. First, build and install Click into some prefix, PREFIX. Then:
cd CLICKDIR/apps/clicky autoreconf -i ./configure --prefix=PREFIX make install
See clicky-css for information on the CSS-like language used to style Clicky diagrams.