One of the things I've been hired to do is write adult themed articles that hit upon specific keywords in an attempt to gain search engine relevancy in a slightly more out of the box way. I've done articles on various fetishes, breaking down their origins and meanings. I've written short how to articles on various subjects, and informative articles on many other things. I've linked a few of these articles below and I think you'll find them a nifty way of approaching keyword relevancy.

How to Approach a MILF
Are You a MILF Hunter?
Pantyhose Encasement Fetish
The Wonders of Pantyhose Sex
Bare Foot Fetish