The Utility Control Point (UCP)
I wonder how many SQL Server DBAs have ever heard of the SQL Server Utility Control Point (UCP) or used the Utility explorer. Until recently I hadn't either. It is a native tool introduced in SQL Server 2008 R2 that lets you easily monitor the health and utilisation of resources. There are a lot of SQL Server sites out there who cannot afford 3rd party monitoring tools and UCP could be a good starting point.
I recommend that you install the UCP on a server other than the servers you are monitoring as it has data collection jobs and a database that you don't want on your production servers. Once installed and you have enrolled your SQL Servers then you have a dashboard from which you can quickly identify whether the instance CPU, database files, storage volumes or computer CPU of managed instances or DACs are - well, over or under utilised. You have the ability to set thresholds about the definition of these utilisation levels. It is easy to configure and use and will give you insight into the usage of your SQL Server resources. I only wish that it would give me information on memory as well.