Menno beat me to it at his CRM blog, but the IFD Tool was published at the below KB article link at Microsoft Support.
Menno sums it up nicely:
There has been a lot of confusion around the Microsoft Dynamics CRM Internet Facing Deployment Configuration Tool, a tool which was mentioned in a document describing Microsoft Dynamics CRM 4.0 Internet facing deployments scenarios.
For the people that don’t know what Internet Facing Deployment means, it is a way to make Microsoft Dynamics CRM 4.0 available to, for example, your home- or offline users without the requirement of needing a VPN connection.
I just bumped into a KB article describing how to use the Microsoft Dynamics CRM Internet Facing Deployment Configuration tool. The tool allows you to configures Internet Facing Deployment (IFD) for Microsoft Dynamics CRM 4.0 after you have already installed or upgraded to Microsoft Dynamics CRM 4.0. The tool is also used when you change the IFD. Another good thing, the tool is available directly from that KB article.
It is not really clear to see the download link, as you can see, you easily read over CRM4IFDTool.zip.