Best plugin for updating multiple WordPress sites

Hi,

Can anyone recommend the ‘best’ wordpress plugin, software or service to update the WordPress version on multiple sites?

I’m being old fashioned and manually updating around 20/30 WordPress sites one at a time in the usual manner, partly because it’s good to login, update the plugins at the same time, have a general look around and make sure everything else is in order. But it’s a drag keeping all the sites I maintain updated in this way.

Any suggestions and experiences?

Thanks,
A