Another thing you could examine are the commercials meant to step away from the norm. For example, JCPenney will have an ad airing in June featuring same sex parents.
Blogging about these types of ads may prove fun/interesting given they are attempts to change the stereotypical face of advertising.
Another interesting topic might be the gender assumptions behind marketing. Why are kitchen cleaners and prepared meals, for example, usually aimed at women while grilling sauces are aimed at men? Thinking about how marketing reinforces gender roles would be a very interesting topic to discuss and might get some responses on a blog.
One thing to blog about would be various marketing strategies that you are able to see on a daily basis. Analyze them. Look at who they are targeting. If you think you are part of the market segment they are aiming at, discuss how effectively they have targeted you. If there's a product you like but you have never really seen marketed, discuss why that is and maybe talk about how you would market it to someone like you.