I have a vast knowledge of analytical chemistry and nanotechnology. I am cursed with the fact that I hate working in the lab. So I am a teacher with a 4.0 throuh all my graduate classes for a Ph.D. I have though about writing but I am not sure what people would want. Whats a good way to market myself?
My suggestion: Go to the lab and do what you know best. People will recognize your service and knowledge.
It doesn't matter what you write about. The way you get better at writing is to do a lot of it. Get a domain and hosting, install wordpress, and strart writing. Look at the pages view stats and that will tell you what people read. If you don'l like the subject it's hard to stay interested.
I agree with the above. Install some blog or CMS software, depending on how adventurous you are in the webmaster and/or programming fields, and start writing. You're not really writing to the same audience as in academia. A lot of people are more forgiving of not following the rules for journal papers. Hold a conversation with the audience, explain something to them. If you won't get questions of people thinking you're crazy, get a speech recognition program like Dragon Naturally Speaking and a microphone, and explain something to them. What's your chemistry knowledge worth? What about people's everyday lives can you explain in fairly simple terms that people would be interested in knowing about? Come up with some ideas people might be curious about, put up a blog, get attention, then put up a poll or prompt article to get more ideas. I think a lot of that knowledge would be very useful, but it is generally not explained at a level that the non chemistry PhD could understand.
You could do some additional research on some current chemisty sites (blog sites specifically) and see what topics people comment on the most, most read articles, etc. This will give you a better idea of what people are interested in.