ESE API at MSDN:  http://msdn2.microsoft.com/en-us/library/ms684493.aspx

New features in ESE for Vista/Server 2008: http://msdn2.microsoft.com/en-us/library/aa964797.aspx

ESE overview http://technet.microsoft.com/en-us/library/aa998171.aspx

Wikipedia article: http://en.wikipedia.org/wiki/Extensible_Storage_Engine