Not sure if this will omit the Report server databases since I am not running one, but from what I have seen, I can omit system user owned databases with this SQL:
SELECT db.[name] as dbname
FROM [master].[sys].[databases] db
LEFT OUTER JOIN [master].[sys].[sysusers] su on su.sid = db.owner_sid
WHERE su.sid is null
order by db.[name]