The still-nameless chess program was my first real attempt at a stnadalone application: it features a mouse-enabled GUI, the ability to read algebraic chess notation, [almost] full move logging, and several different output methods.
Although it is still simple at this stage, the engine itself is well-tested and functional.
It has a Subversion repository at http://www.bandstand.org.uk/~benm/chess-svn/ which has gone through 81 revisions to date.
The Makefile builds a maximum of three executables, each from two common C files, one header file, and a third C file that differs between them. ui_ansi.c, and the Makefile target chess-ansi, should build most places, and only uses libc as far as I know.
ui_allegro.c and ui_cairo.c both use external libraries (Allegro and, equally unsurprisingly, Cairo), although the latter never made it to a usable state.