Sage Quick Reference Cards
Sage Quick Reference by William Stein (March 2009) - quickref.pdf download (and the source quickref.tar.bz2 download)
Sage Elementary Number Theory Quick Reference by William Stein (April 2009) - quickref-nt.pdf download (and the source quickref-nt.tar.bz2 download)
Sage Calculus Quick Reference by William Stein (April 2009) - quickref-calc.pdf download (and the source quickref-calc.tar.bz2 download)
Basic Math by Peter Jipsen, version 1.1 (January 2008) - sage-quickref.pdf download (sage-quickref.tex download)