For those who have been spending a lot of time listening to the White Horse Inn, I think Frame's article (available here) may be a challenging and important counter-point.
So the definitions that sharply separate law and gospel break down on careful analysis. In both law and gospel, then, God proclaims his saving work, and he demands that his people respond by obeying his commands. The terms “law” and “gospel” differ in emphasis, but they overlap and intersect. They present the whole Word of God from different perspectives. Indeed, we can say that our Bible as a whole is both law (because as a whole it speaks with divine authority and requires belief) and gospel (because as a whole it is good news to fallen creatures). Each concept is meaningless apart from the other. Each implies the other.
Thanks to Ronald W. Di Giacomo and Steve Hays for bringing this to my attention.