Given a variety X embedded in a projective space PV , the (k - 1)-st secant variety of X, denoted kX, is the closure of the union of all (k -1)-spaces spanned by k points on X. We usually require that X spans PV , so that kX = PV for k sufficiently large. We often work with the cone C in V over X rather than with X, and write kC for the cone over kX. Secant varieties appear in applications as diverse as phylogenetics [2, 5, 12], complexity theory [10, 11], and polynomial interpolation [1]. The references in this note are by no means complete, but they themselves contain many further relevant references