<p>What is .net dynamic data and why would I use it?</p>

From
ScottGu's Blog
a great article on how to use Dynamic Data.
One of the cool new features is something we call "ASP.NET Dynamic Data Support". In a nutshell this enables you to
  really quickly build data driven
  web-sites that work against a LINQ to
  SQL (and in the future LINQ to
  Entities) object model - and
  optionally allows you to-do this
  without having to build any pages
  manually.
See this
screencast
. It is very enlightening.
From more official
ASP.NET Dynamic Data site
:
ASP.NET Dynamic Data provides a
  framework that enables you to quickly
  build a functional data-driven
  application, based on a LINQ to SQL or
  Entity Framework data model. It also
  adds great flexibility and
  functionality to the DetailsView,
  FormView, GridView, and ListView
  controls in the form of smart
  validation and the ability to easily
  change the display of these controls
  using templates.