Is it quite common at most Orthodox shuls for there to be a women's shiur presented by a female? What topics would generally be discussed?
It's hard to say what's true of "most" Orthodox synagogues, but certainly most I've been in have classes for women presented by women, yes. Topics have included Scripture (parashas hashavua or Nach), hashkafa (Weltanschauung), halacha (often related to the time of year), and others: basically most of the non-textual topics covered by men (who speak for men or for women or for mixed crowds). Occasionally they have been based on texts (usually excerpts photostatted and distributed) and covered halacha or similar topics more analytically, especially in more 'modern' synagogues.