Foucault has been interpreted in the US as a pretentious standard-bearer of postmodernism - as an almost "evil" figure who threatens to undermine the foundations of Western knowledge with his problematisation of conceptual categories. It doesn't help that his work has been taken up to justify just about any subversive perspective, whether well-conceived or not. This is only a pitifully small perspective on the man and his work. Foucault should be seen first as a historian, not a philosopher; second, his work should be lauded for the contribution it makes to Western knowledge rather than the superficial "threats" it makes to perspectives whose time has come in any event. Every revolution of perception has been accompanied by vociferous resistance, yet a great many of those sounding their disapproval loudly probably don't really understand what the late Michel was really on to.
The Birth of the Clinic, MF's most accessible work, is a well-researched, brilliantly interpreted account of the development of the clinical "gaze" in the wake of modern medical knowledge and practice. Foucault problematises the institution of the clinic, showing how clinical perception is the result of a historically specific constellation of knowledge and power. His ultimately emancipatory analysis is substantiated every step of the way with textual and historical examples. No metaphysics here, just a radical questioning of the nature of knowledge within institutional practice.
So, sorry (Objectivists!) if this is too much to handle. It's good research, plain and simple. Don't dismiss Foucault as a lightweight postmodernist - try to see him where he would situate himself, in the tradition of reflexive historical sociology.