How can I start using Freestyle? Blender 2.67 is out, and one of its main features is the long-awaited Freestyle integration.

I'd like to try out Freestyle, but it doesn't appear in the "Render Engine" dropdown. I assume some assembly is required. What will I need to start using Freestyle on Windows and Linux?
You're right, it doesn't appear in the render engine dropdown.

In version 2.66 it is in Render tab > Post Processing > Freestyle.

Thanks to RagnarSun, in 2.67 (and 2.67a) it is in Render > Freestyle.