There are really a whole bunch of great resources out there that help the community get up & running with LINQ.

Personally, with all the additional providers that I've seen (Qak Leaf List) - several of which I see great use for - LINQ to SharePoint and LINQ to LDAP / LINQ for AD.

In regards to tools, LINQ Pad is the tool that allows you to toil with the syntax, etc.

LINQ Pad

And now, here's a good 100+ pages on LINQ syntax in C# 3.0.

Book Preview: C# Query Expressions and Supporting Features in C# 3.0