Books are heavy, instead consider going digital:
MIT OpenCourseWare: Mathematics, Robotics (fun & hardcore), Languages, and for some-nirvana (difficult but, with the gift of military discipline, do-able)
Calculus references
Google Calculator
Save some space in your ruck for a graphing calculator. If you like RPN and a tough/quality product try a HP if you like a easier to use calculator try a TI
How about the Australian School of the Air as a case study?
Bookmarks