system-databases

Is it possible to query the system databases in SQL server without using the names?

When doing a query over several databases in SQL server (2005+) I find it sometimes necesary to exclude the system database (master, model, tempdb, msdb and distribution) Is there any OTHER way to filter these besides where name not in (''master', 'model', 'tempdb', 'msdb', 'distribution') I've looked at sys.databases and master.dbo...