What are some essay topics in relation to the themes of gender and power in Shakespeare's Macbeth?

Gender and power are closely tied in Macbeth, and they can be examined from a variety of perspectives.
At the most superficial level, we can examine who has "power" and who does not. Arguably, the most powerful character is Macbeth, a man, yet he gained his power (being king) from the prophecies of the witches and the encouragement of his wife. While Macbeth ostensibly occupies the power in a "manly" fashion (murder), we might question whether he was actually installed there by female power, as a puppet ruler, beholden to female provocations. Perhaps Macbeth holds the traditional male power because he has to (the role being a male one), and because it is politically expedient for him to do so, and because those who manipulate him seek to use that power for their own gain. This also lends further significance to Macduff's birth by cesarian section; Macbeth is defeated by someone who is "not of woman born", perhaps implying that "true" male power, or at least, a lack of female genesis, was the only way to defeat the largely "female" force that put Macbeth into power.
We should also examine how carefully Shakespeare constructs the idea of being female, as opposed to the reality of it. There are numerous occasions where the female nature is directly addressed in stereotypical terms;

O gentle lady, 'tis not for you to hear what I can speak: The repetition, in a woman's ear, would murder as it fell.

This implies that the nature of women is fragile. Yet on multiple occasions, and especially in private, Lady Macbeth depicts herself in far more brutal terms, in contrast to and especially in contradiction to the aforementioned stereotypes;

I would, while it was smiling in my face,
Have plucked my nipple from his boneless gums
And dashed the brains out, had I so sworn as you
Have done to this.

Lady Macbeth is not only defying the expectations of her gender, but using them to enhance her argument. By painting herself as a violent monster, or acting as if she wishes she were one, she simultaneously reveals the depths of her craving for power (being so willing as to defy societal expectation and her own feelings) as well as bringing tension and immediacy to her arguments with Macbeth; he must commit the murders because she cannot.
 
Finally, we can look at these roles from outside of the play itself; how did the realities of Shakespeare's time affect his writing, and how are our modern sensibilities affecting our interpretations of his work? Consider the lack of female actors, for example, and the fact that it was men portraying women as a matter of course during that time period. Today this might be attacked as an implication that women are incapable of performance art, whereas at the time it may have simply been a practical matter, and one as socially acceptable as we consider it unacceptable today. To this point, we can analyze gender and power in the play on what we might call a spectrum of intent; if we are upset by the fact that Lady Macbeth was played by a man, why does this upset us, and how does the play reflect and contradict our current ideas of gender and power?
http://teachers.yale.edu/curriculum/viewer/initiative_07.01.03_u