Loonwatch has done the best scholarly research on Apostasy in Islam I have ever seen. These Guys rule. Careful reasoned attacks of the Loons on both sides of this controversy. Among its many useful resources is a link to a petition which renounces the idea that Islam requires death for Apostates. This petition was signed by over a hundred prominent Muslim clerics. Here's an important quote from that petition.
Undeniably, the traditional position of Muslim scholars and jurists has been that apostasy [riddah] is punishable by death. The longstanding problem of the traditional position, as held by Classical jurists or scholars, can be explained and excused as not being able to see apostasy, an issue of pure freedom of faith and conscience, separate from treason against the community or the state. However, the accumulated experience over the history in terms of abuse of this position about apostasy even against Muslims as well as the changed context of a globally-connected, pluralistic society should help us appreciate the contemporary challenges in light of the Qur'anic norms and the Prophetic legacy. In this context, while the classical misunderstanding about this issue of apostasy is excusable, the position of some of the well-known contemporary scholars is not