Found this which looks very nice: http://weblogs.asp.net/scottgu/archive/2007/05/19/using-linq-to-sql-part-1.aspx
Seems to cover a lot of the different aspects that you’ll need to understand about LINQ to SQL.
And here are some videos on the concept: http://mtaulty.com/CommunityServer/blogs/mike_taultys_blog/archive/2007/05/10/9322.aspx