I am building a simple Saas application. The skeleton of what I have so far is here http://www.pomsapp.com/
I plan to refactor and revise as needed. Technologies used so far.
Language - Ruby (framework Sinatra - not rails)
Responsive grid - Zurb Foundation http://foundation.zurb.com/docs/ - not blueprint
CSS generated by Sass and compass (zurb needs that)
Rendering - haml (no erb, no slim)
Help desk integration - http://www.freshdesk.com
Authentication - sinatra-warden (similar to devise) in stand alone version. Also added integration with google apps marketplace (https://www.google.com/enterprise/marketplace/)
Automated testing - rspec and capybara
Deployed on Amazon aws.
Database currently sqlite3 using DataMapper as ORM. Seriously considering to use Redis as db and Ohm as ORM (see http://monkrb.com)
Payment - now using stripe. see https://stripe.com/ - very easy configuration of trial periods, payment plans, coupons etc.
High level description: http://www.johnvarghese.com/pomsapp-a-saas-web-application-for-purchase-order-management-draft-1-part-2/
Skills: rendering, amazon