SPMetal is a part of the new SharePoint development toolset that allows you to generate the definitions for use with Linq to SharePoint. In the current release SPMetal is a command-line tool. At least it was, because using Imtech Get SPMetal Definition Extension you can use it from your SharePoint Server Explorer in Visual Studio!
Imtech Get SPMetal Definition Extension is an extension for the new Visual Studio SharePoint development tools. Upon installation it adds an extra menu item called Get SPMetal definition to every site node in the SharePoint Server Explorer.
This menu option executes the SPMetal tool with the URL of the Site currently selected in the SharePoint Server Explorer. The generated definition is being displayed in Visual Studio so that you can easily add it to your project.
At this moment the Imtech Get SPMetal Definition Extension supports only C#. If you are a VB developer and you like this extension, just let me know and I will add the option to generate VB code as well.