I am going to give some links that go from simple and robust to more advanced. I used these when I wrote a small demo of a cloth sim, and of all the resources I checked out, these were the best/most fun:
Physical modelling in general:
http://www.cs.cmu.edu/~baraff/sigcourse/index.html
Particle simulation:
http://www.darwin3d.com/gdm1999.htm
Stable and easy to understand implementation:
http://www.ioi.dk/Homepages/tj/publications/gdc2001.htm
More advanced integration schemes:
http://www-2.cs.cmu.edu/~baraff/papers/sig98.pdf
More real time advanced integration:
http://www-grail.usc.edu/pubs/DSB_GI99.pdf
Also check these out:
http://www-grail.usc.edu/
http://www.cs.caltech.edu/~mmeyer/Research/Cloth/
http://www-grail.usc.edu/pubs/DMB_chapterBook.pdf
http://miralabwww.unige.ch/ARTICLES/JWS97-B.html
/Joakim