If you're looking some important links to use LINQ to SharePoint technology for SharePoint 2010:

Microsoft SharePoint LINQ API


http://msdn.microsoft.com/en-us/library/ee541836(v=office.14).aspx

Developer overview video

http://msdn.microsoft.com/en-us/sharepoint/ee514561.aspx

SPMETAL


SPMETAL Home

http://msdn.microsoft.com/en-us/library/ee538255(v=office.14).aspx

How to: Use SPMetal

http://msdn.microsoft.com/en-us/library/ee538587(v=office.14).aspx

Type Mapping: From LINQ to SharePoint Provider to .NET

http://msdn.microsoft.com/en-us/library/ee536245(v=office.14).aspx#BKMK_LookupFields

SPMetal Default Code Generation Rules

http://msdn.microsoft.com/en-us/library/ee537010(v=office.14).aspx

Overriding SPMetal Defaults with a Parameters XML File

http://msdn.microsoft.com/en-us/library/ee535056(v=office.14).aspx

Screencasts & tutorials


Channel 9: LINQ to SharePoint

http://channel9.msdn.com/learn/courses/SharePoint2010Developer/LINQtoSharePointUnit/

Channel 9: SharePoint courses

http://channel9.msdn.com/learn/courses/SharePoint2010Developer/

Microsoft SharePoint Conference 2009

http://www.mssharepointconference.com/Pages/default.aspx

LINQ to SharePoint 2010 tutorials

http://cglessner.blogspot.com/2009/10/early-look-at-linq-to-sharepoint.html

http://sergeluca.spaces.live.com/Blog/cns!E8A06D5F2F585013!7312.entry

http://sergeluca.spaces.live.com/blog/cns!E8A06D5F2F585013!7105.entry