Dino Dai Zovi has a fairly comprehensive list of the security-related features he hopes Snow Leopard will implement. Real ASLR (address space layout randomization). Full use of hardware-enforced Non-eXecutable memory (NX). Default 64-bit native execution for any security-sensitive processes. Sandbox policies for Safari, Mail.app, and third-party applications. Mandatory code signing for any kernel extensions. Read the rest of the article for [...]

According to this screenshot from a Snow Leopard Developer Preview, an Intel processor is required. This could mean that Snow Leopard will not support legacy machines (ie. PowerPC), or it could simply mean that the Developer Preview only supports Intel processors. Time will tell.

From Apple’s Snow Leopard page: Since 2001, Mac OS X has delivered more than a thousand innovative new features. With Snow Leopard, the next major version of the world’s most advanced operating system, Mac OS X changes more than its spots, it changes focus. Taking a break from adding new features, Snow Leopard — scheduled to [...]