Roman Bartak has an On-line Guide to Constraint Programming
<http://kti.ms.mff.cuni.cz/~bartak/constraints/>

V. Kumar, "Algorithms for Constraint-Satisfaction Problems: A Survey,"
AI Magazine 13(1):32-44, 1992.  (A postscript version
<http://www.cs.unh.edu/ccc/archive/constraints/archive/kumar.ps> is
available.  It differs slightly from the published version.)

David McAllester's lecture notes on constraint satisfaction search
<http://www.cs.unh.edu/ccc/archive/constraints/archive/dmac.ps>
[postscript].

Constraint Logic Programming
<http://www.cs.unh.edu/ccc/archive/constraints/archive/byte.html> by Dick
Pountain. 
Reproduced with permission from BYTE  <http://www.byte.com/> magazine,
February 1995; converted to html by Michael Jampel.  (BYTE has now put
their version  <http://www.byte.com/art/9502/sec13/art3.htm>
of the article on the web.)

E. Tsang <edward@essex.ac.uk>, "Foundations of Constraint
Satisfaction", Academic Press, 1993.  ISBN 0-12-701610-4.  
(Out of print, but available from the author
<http://cswww.essex.ac.uk/CSP/edward/FCS.html>.)

Also see the articles on Constraint Networks (pages 276-285) and
Constraint Satisfaction (pages 285-293) in Shapiro's Encyclopedia of
Artificial Intelligence.