Weblogs Forum: Fluid Programming in Lucid -- good examples, and very good links.
Wikipedia article (yet a stub, but useful links).
The most detailed online material on the details of this language I could find: Raganswamy Jagannathan, Chris Dodd. GLU programmer's guide (dowloadable as the 4th paper of GIPSY Publications). The first pages seem to discuss other problems, but it is worth of read further, because a detailed description of Lucid's syntax and semantics is hiding inside this paper (section 3.1.2 on pages 22--38). This paper is part of the Gipsy Project Home Page (GIPSY: A General Intensional Programming System).
A fast-food implementation:
A better implementation could be written using the arrow library available at the Downloads page of Arrows: A General Interface to Computation written by Antony Courtney, Henrik Nilsson and Ross Paterson.
A professional approach based on comonads: see The Essence of Dataflow Programming paper.