megmorsie uses CodeIgniter
I used CodeIgniter while working at KHM Travel Group. It was the system we used for an affiliate-based site called TravSearch, which I later replaced with a WordPress Multisite. I developed a .csv upload form to transfer all the information from the affiliate table of CodeIgniter to the user and options tables in WPMU.
datapile uses Play
Play is a central framework/component/library (not sure what to call things these days) in Scala. We <3 Scala, and therefore we <3 Play.
Play is on of several frameworks we are prototyping and vetting for various public-facing websites, and may ultimately be the framework behind the main datapile.io website.
gllona uses CodeIgniter
CodeIgniter is the MVC framework used for the PHP coding. Also, validation criteria for (database) table fields are the provided by CodeIgniter, and signatures for others are derived from those.
elo80ka uses Play
I used Play to build a configuration UI for the service, which let you create and manage the menus (a hierarchical tree of options and actions).
delbin uses CodeIgniter
It is super easy to do things in PHP using codeigniter. Used the MVC architecture to create different types of pages and modules.