Sarah Stroud has written a helpful summary of the literature on Weakness of Will for the Stanford Encyclopedia of Philosophy, published in May 2008. She sets out the basic philosophical problem -- how is weakness of will possible? -- then sets out Davidson's solution, and some problems with Davidson's view. She moves on to the question of whether weakness of will is always bad, paying attention to Nomy Arpaly's arguments that it can be rational. She concludes with a brief discussion of Richard Holton's refiguring of the debate, where he argues that weakness of will is not acting against one's values, but rather a too easy changing of one's mind and giving up one's resolutions, followed by Alison McIntyre's recent suggestion that when one is weak-willed and acting against one's values, it is better to be clear that is what one is doing, rather than to rationalize one's actions.
Holton (pictured) has extended his work on weakness of will and strength in his forthcoming book, Willing, Wanting, Waiting, (available in pre-print on his home page). His work is wonderfully clear, and is backed up by recent work in social psychology, such as the research by Roy Baumeister on self-control and ego-depletion. In a recent paper, Holton, with Stephen Shute, applies his ideas to a legal context, arguing that loss of self control needs to be taken seriously as a criminal defense. ("Self-Control in the Modern Provocation Defence")
Holton's work here has already given rise to other published discussions. The journal Criminal Law and Philosophy has a couple of accepted articles related to this: Stephen Garvey has a paper on "Dealing with Wayward Desire," and Vera Bergelson has a reply to Garvey, "The Case of Weak Will and Wayward Desire." Garvey, following Holton, argues in favor of the idea that sometimes people are unable to exercise self-control and this should be a valid legal excuse for criminal action, while Bergelson argues that such sympathy for the offender has no place in the criminal law.