mainwP is a very useful tool for managing your whole WordPress site network. I currently use it for 70 WordPress sites and it saves me a lot of time. There are a lot of extension available for MainWP but the most important two are the code snippet extenionto execute code on the child site and the bulk setting extensin to post keys with forms post data to the child sites to configure any sort of plugins settings page. This is the most amazing thing of MainWP. You can easily create settings template (called “key”) and populate it’s data to all your sites.
See the following ressources for more useful stuff, templates, keys and plugins. I will update the list as I find new stuff.