If you have never used Vagrant to isolate your dev environment you should. While not explicitly necessary for ruby and rails projects it helps not only provide a reproducible dev environment but also to share your reproducible dev environment.
I used to use virtualenv for most of my python projects but have now migrated to vagrant and Chef.
My first image ready to share is my rails image based on a precise64.box base.
I will follow up with my Bioinformatics image when i get a chance