Several sources of material:
http://ourworld.compuserve.com/homepages/T_Gooch (system study guide)
http://www.utem.com (system/sim study guide)
http://www.avishop.com - (click on aviation supplies, then system study guides)
http://www.firstnethou.com/fmcman/home.html
(Detailed FMC User's Guide)