If you haven't seen the announcement, a new version of the SQL Server 2005 Best Practices Analyzer is available for download (dated July 2, 2007). The BPA will run on Windows XP, 2003, and Vista. It requires the Microsoft .NET Framework 2.0 as well as the SQL Server 2005 client tools.
If you're not familiar with the BPA, it uses defined templates on best practices to analyze the configuration of both the server and any databases you might select. For instance, if your server is set to Mixed Mode authentication and not Windows only authentication mode, BPA will flag this configuration. It's a great tool to run to take a look at where your SQL Server differs from best practices and make a determination if such a deviation is acceptable (for instance, a 3rd party app uses a SQL Server login, therefore Mixed Mode is required).