This git repository helps you get up and running quickly w/ a Sinatra installation on OpenShift.
Create an account at http://openshift.redhat.com/
Create a ruby-1.8 application
rhc app create -a sinatra -t ruby-1.8
Add this upstream sinatra repo
cd sinatra
git remote add upstream -m master git://github.com/openshift/sinatra-example.git
git pull -s recursive -X theirs upstream master
Then push the repo upstream
git push
That's it, you can now checkout your application at:
http://sinatra-$yournamespace.rhcloud.com