Visio 2007 has made great strides and is relative inexpensive.
You can create relational diagrams, reverserve engineer and existing databas to generate an ERD, etc
For better, quicker answers on T-SQL questions, click on the following...
http://www.sqlservercentral.com/articles/Best+Practices/61537/
For better answers on performance questions, click on the following...
http://www.sqlservercentral.com/articles/SQLServerCentral/66909/