I wrote a pile of scripts that scraped both sites, parsed and cached the data, and displayed it on a map. I was able to set search criteria based on location, and kludged it so that if something good came up, the system would automatically email the landlord if they made the email available, text them if they left a number, and text me a notification with a link.
The scraper eventually got pretty fancy as I expanded the service across multiple cities - it self-throttled and self-scheduled, based on the average frequency of postings on each platform in each city at a given time of day. The repost detector was working pretty well too, it added a layer of data to the results (eg, "this rental was re-listed 12 times in the past two weeks).
Once I found a place I liked, I made the site public and shared it with some friends, and it didn't take long until I was seeing steady daily use. The site even won an award from CIRA.ca!
I wrapped things up when I learned of Craigslist suing Padmapper for scraping their data. I wasn't monetizing, it was a cool project, but it felt like it was done.
