Starling is a great (at least for small projects) and simple message queue, however, it doesn't actually manage or start workers that consume the queues. Workling does this for Rails projects, but doesn't work for pure ruby applications, neither for Sinatra.
Before I fork workling, or create my own custom one with threads/fork, is there another project that does it?
Look at resque. It is framework agnostic and contains rake tasks to start an arbitrary number of workers to consume your queues. It uses redis lists for the queue backends, so you will need to install and manage that.