Select Faces By Normal is is one of my recent personal scripts. Select faces by normal in the given XYZ positive/negative axis. Work with base poly/mesh, edit poly/mesh modifiers, mesh select modifier.
NOTE: The current macros is not a replacement of the Graphite Tools (new in Max 2010) "Select By Normal" utility. This script have more flexible functionality (and fills my needs). Also if relevant, you can use that script in older Max versions.