Business Connectivity Services is the new version of the SharePoint 2007 technology called Business Data Catalog. The base of this technology is now available in SharePoint Foundation 2010 which is the free version of SharePoint. This means you can build an External Content Type in Visual Studio 2010 and deploy it to SharePoint Foundation 2010 and the code in the External Content Type retrieves the data which is then shown in a standard SharePoint list.
Great technology. I wanted to link to the trick to making the External Content Type deploy from Visual Studio 2010 to SharePoint Foundation 2010 which doesn't affect SharePoint Server 2010.