I realized one day that craigslist ads could be made way prettier by adding a bit of HTML, so I made a small business for myself making custom ads and taking care of the day-to-day posting for a few car dealerships in the area.
Once I learned a bit of Ruby, I was able to create a little program that cut my work time by two thirds. It crawls through the web page I point it to, grabs the info I want, and formats it into something that will be nice to look at once I put it up on Craigslist.