Sweet article on converting Lists to DataSets

Complete with code...

http://blog.lozanotek.com/archive/2007/05/09/Converting_Custom_Collections_To_and_From_DataTable.aspx

Excellent article on Linq to Sql

Has pretty much everything you need to know:

http://weblogs.asp.net/scottgu/archive/2007/05/19/using-linq-to-sql-part-1.aspx