Ju-Yi Kuo from our team has started blogging about advanced mapping scenarios supported by Entity Framework.

Part 1 of his EF Mapping Advisor series is online at http://blogs.msdn.com/juyik/archive/2008/05/21/ef-mapping-advisor-1-the-language-of-mapping-part-a.aspx and it explains TPT (table-per-type) mapping strategy.