Creshaw wrote a great series of articles on writing parsers. Truly a great series of articles. As influential to me as Stevens series of books on TCP.
Unfortunately the articles used Pascal. Which is a great language and all, but I had to implement some parsers in C, so I translated the code to C, here are the files:
I seem to have lost these translations I did years ago in a hard drive crash, but I was able to save the first three by finding them on The Wayback Machine (www.archive.org).