http://www.ushmm.org/outreach/nrule.htm the most thorough. Dr. Steven Feinberg extracted some of this material for his presentation to us at the U.S. Holocaust Memorial Museum's seminar for teachers.
http://remember.org/shoah/timeline.html
http://remember.org/educate/mtimeline.html
http://motlc.wiesenthal.com/resources/education/timeline/index.html Simon Wiesenthal Center Multimedia Learning Center
http://www.melazerte.com/library/timeline.htm an excellent teacher-developed timeline
http://library.thinkquest.org/12663/timeline/?tqskip1=1&tqtime=0610 The Holocaust: A Tragic Legacy
http://www.holocaustchronicle.org/
http://fcit.coedu.usf.edu/holocaust/timeline/timeline.htm