It's marvelous to see articles on this worry of ours appear so prominently (and, it seems, more frequently). Especially since it is not uncommon for my colleagues in other humanities and social sciences to be utterly and completely surprised when they find out that the gender make-up of my department is typical for the discipline as a whole. (The economics department down the hall is the same size but has more women.)
One thing we need to (and have been) doing is to 1) identify (possible) causes of the gender disparity; 2) identify strategies to remediate it; 3) work to see these through; and 4) find ways of evaluating their success.
Regan Penaluna, the article's author, is clearly committed to doing this. Having identified the male (and sometimes misogynist) content of philosophy classes as a possible cause, she's writing a book on early women philosophers. The continued entrenchment of a canon in philosophy is a clear difference between our classes and what's going on in English Lit!
At the same time that we pursue strategies to diversify the authors and content that we teach (How many women were on the last syllabus you put together?), I think it's vital to address possible social causes.