http://www.microsoft.com/technet/scriptcenter/scripts/sql/sql2005/default.mspx

Sample scripts and stored procedures for managing and working with SQL Server 2005.

Buffer Cache
Sample scripts and stored procedures for managing and monitoring the SQL Server buffer cache.
 
CPU and Optimization
Sample scripts and stored procedures for optimizing CPU performance in SQL Server.
 
Indexes and Indexing
Sample scripts and stored procedures for working with SQL Server indexes.
 
Input/Output
Sample scripts and stored procedures for managing and monitoring input and output in SQL Server.
 
Performance (General)
Sample scripts and stored procedures for managing and monitoring general performance issue in SQL Server.
 
Procedure Cache
Sample scripts and stored procedures for managing the SQL Server procedure cache.

SQL Text
Sample scripts and stored procedures for working with SQL text.
 
SQLOS
Sample scripts and stored procedures for working with the new SQL Server Operating System Layer.
 
Tempdb
Sample scripts and stored procedures for working with the tempdb system database.
 
Transactions and Logging
Sample scripts for working with SQL Server transactions and locks.
 
Waitstats
Sample scripts and stored procedures for working with SQL Server waitstats.