The precursors to TeX (1978-82) and Metafont (1979-83) are good examples of complete, non-trivial Sail programs. Both were written by Donald Knuth; the sources for prototype-TeX are in http://www.saildart.org/[TEX,DEK] (see the latest rev of each TEX*.SAI file); while prototype-MF is in http://www.saildart.org/[MF,DEK]