I've searched around Oracle's sites and cannot find the actual executable to download. I get sites that point to older versions, or to the source of Scene Builder instead. I'm looking for the actual windows/mac executable installer for the latest version of Scene Builder.
Here are both version 1.x and 2.x scene builders http://www.oracle.com/technetwork/java/javafxscenebuilder-1x-archive-2199384.html
This project was moved to openjfx project. So you can get the latest source code and any other version from http://hg.openjdk.java.net/openjfx
This is the scene builder for jdk 8u40 http://hg.openjdk.java.net/openjfx/8u/rt/file/5fc0ddb42776/apps/scenebuilder