According to The Jerusalem Post, Natan Sharansky has quit the Sharon government, in protest against Israel's Gaza pullout. He said that Israel's military move was premature, and should instead follow full Palestinian democratization. He told interviewers: "I have always believed that the disengagement plan is a heavy price to pay and encourages terrorism." (thanks to Little Green Footballs for the tip)
Sharansky's resignation letter can be found on Winds of Change.