ConfigMgr'07 site server database is one of the only supported site role in clustered configuration in ConfigMgr'07. Though I have not configured clustered DB in production so far, as we did not have critical business requirement for having clustered ConfigMgr'07 site server DB and having extra hardware for the same, but since it is supported and may be needed for other customer so sharing some references and to do list for considering this in production which will increase high availability and reduce single point of failures.
1. Use the setspn.exe (part of suptools.msi from the Windows Server 2003 Installation media) to publish the SPN of your virtual SQL Server cluster (Important: Publish both the NetBIOS and the FQDN) - http://technet.microsoft.com/en-us/library/bb735885.aspx
2. Add the machine account of the primary site server machine to the Local Administrators group of each Windows Server cluster node computer. This is required to allow the site server to install and configure settings later.
3. Check the Database collation settings of the tempdb database on the SQL Cluster (ensure you have the same settings like on the site server which hosts the DB at present). This is very important to check this before you move the database to the cluster.
4. If the Microsoft Systems Management Server (SMS) Provider is located on a remote SQL server, the SMS provider must be moved to the local site server or another computer not hosting a SQL Server cluster node before moving the site database.
5. To move the database finally check the link How to Migrate the Site Database to a SQL Server Cluster Instance http://technet.microsoft.com/en-us/library/bb632383.aspx
More information available:
SQL Server Preparation for Setup
How to Configure an SPN for SQL Server Site Database Servers
How to Install Configuration Manager Using a Clustered SQL Server Instance
How to Migrate the Site Database to a SQL Server Cluster Instance