If you are trying to learn T-SQL, you can't go very far wrong picking up Itzik Ben-Gan's book. He has a fundamentals book and the Inside book.
I don't know of any free resource that's going to do a good, thorough, and accurate job of teaching t-sql. You'll either have to bounce around a lot or find a for pay resource. Sorry. But it's true.
"The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood"
- Theodore Roosevelt
Author of:
SQL Server Execution Plans
SQL Server Query Performance Tuning