Padrino supports the following ORMs out of the box: mongoid, activerecord, datamapper, couchrest, mongomatic, ohm, ripple, sequel. Take a look here: http://www.padrinorb.com/guides/generators

Padrino is just a Sinatra app with a very basic skeleton and some added functionality. Almost all the pieces are modular and doesn't have many requirements from the start.