Janther is a website that hunts for apartments for you. You just tell us what you're looking for, and when you're free to view apartments. Whenever an apartment gets posted online that matches your preferences, Janther will set up a viewing appointment for you.
To give our users access to every apartment posted on Craigslist, we used a custom client I wrote to interface with the 3taps API. I later open sourced that client, and it has been downloaded over 18,000 times since.
I used Django to build our API and task scheduler, which periodically pulled down new apartment data. The frontend, where users could set their apartment preferences, was written in Angular.js.