control over multi wp sites

Hi

I have recently discovered wordpress and have built a couple of wp sites for clients, even though I dont have one for myself as yet.

I was wondering if there was a plugin that I could use to maintain all the wordpress sites I create from one panel?

I realise I would have to have a wp site of my own to be able to use the plugin (Im working on building it now)

Im just not sure what I would call the plug in I am after so I could search for it, or if anyone can recommend me a good one.

Cheers