We at Tag1 have used the Cacti Memcache templates many times. (http://dealnews.com/developers/cacti/memcached.html) They have become a staple for us and many others. However, we and one of our clients have had issues making them work for monitoring multiple Memcache instances (running on different ports) on the same host. It is possible to make this work with the vanilla templates, but it is a bit difficult.
Because of this, we have created a re-roll of the latest templates that allows you to add multiple templates to a host and set the port on each of them. This work was kindly sponsored by http://www.looforyoo.com/.
These graphs work exactly the same as the vanilla ones, but there is a port field to fill out when you create the graph. You can add multiple graphs to the same host by going through the create step multiple times. (i.e. selecting the graph in the create graph drop down box and pressing create)