Here are a few that I find very useful:
- SQL Server Best Practices - Microsoft SQL Server White Papers and Best Practices
- vyaskn - A mixture of articles From DBA to Developer
- Backup, Integrity Check and Index
Optimization
- SQLServerCentral Scripts - Scripts for most most DBA tasks and more
- Script Repository: SQL Server 2005 - TechNet Script Center
- Scripts and Tools for Performance Tuning and Troubleshooting SQL Server 2005
- SQL Server Query Processing Team - Hardcore advice from the MS SQL optimisation team
- Common Solutions for T-SQL Problems
- Davide Mauri's Index Scripts
