Today, Microsoft released the Forefront Threat Management Gateway Best Practices Analyzer, or ForeFront TMG BPA for short. Like other Best Practice Analyzer tools, this tool is to analyze the configuration and health of systems, based on predetermined best practices rules. The tool reports any issues, after which you can take action. Note that the installation also contains a tool, titles BPA2Visio, to (as you can probably guess) generate Visio drawings using the information found in TMG. BPA2Visio requires a Visio installation. You can download ForeFront TMG BPA, which is labeled version 8.0.1, here.
Be advised that TMG BPA only works on TMG, not on ISA installations. For ISA analysis, use ISA BPA which can be downloaded here.