A short-messaging social network
The messages have a limited length, and you can follow folks, and be followed by folks. It's similar to App.net and Twitter.
Free, but invite-only
Our community is small, and sustainable as a hobby. Hopefully this can help it be an enjoyable, useful place.
The utility of pnut.io is its extensibility. You will need an app from a developer to do even the simplest things (creating a post!), but developers have the potential to build programs that let you do more creative things, too.