Here are couple of blog/forum entries I find useful and fun to read outside of the great Books Online resource:
1. http://www.bennadel.com/blog/938-Using-A-SQL-JOIN-In-A-SQL-UPDATE-Statement-Thanks-John-Eric-.htm
2. http://www.sqlservercentral.com/Forums/Topic493913-338-1.aspx
3. http://www.bennadel.com/blog/938-Using-A-SQL-JOIN-In-A-SQL-UPDATE-Statement-Thanks-John-Eric-.htm
4. http://www.sqlteam.com/forums/topic.asp?TOPIC_ID=100415