D&P is good, but I'd suggest as a first read the first volume of the History of Sexuality. It's a more concise introduction to his thought on the role of power in formation of subjectivity, rather than as something that is top-down. I've seen too many beginners in Foucault get wrapped up in notions like the panopticon in D&P and miss more substantial elements of his thought.

I'd also recommend his essays such as "What is Enlightenment?" for beginners (online: http://foucault.info/documents/whatisenlightenment/foucault....). Even though it may require a few reads, it helps to consider his thought in relationship to thinkers like Kant (who heavily influence linguists such as Chomsky, and Chomsky's view of human nature), and perhaps more importantly it indicates the important role that he considers power to have in the formation of knowledge and subjectivity.