rstat.us is a microblogging site built on top of the ostatus protocol.
Just do this:
$ git clone https://github.com/hotsh/rstat.us.git
$ cd rstat.us
$ heroku create
$ git push heroku master
Bam!
This is nowhere near done. Jump on Freenode and ping 'steveklabnik' if you want to contribute in some way.
You need MongoDB (www.mongodb.org). On Mac OSX, I had to unzip the tarball and do the following:
$ cd mongodb-osx-x86_64-1.8.0
$ sudo mkdir /data && sudo mkdir /data/db
$ sudo bin/mongod
Then do the same as above:
$ git clone https://github.com/hotsh/rstat.us.git (or your own fork, if applicable)
$ cd rstat.us
But instead of using heroku, run it with sinatra:
$ gem install bundler && bundle install
$ rackup