Udacity

Udacity is a platform with a strong focus on technology, with a small but well-crafted selection of courses. If you’re looking to break into data science (called the “sexiest job of the 21st century“), Udacity’s data science program has an impressive roster of teachers from companies like Salesforce and Facebook.

Udacity’s pricing structure allows you to pay monthly for your courses; if you decide to drop a program before completing it, you pay for the course up to that point, rather than the whole thing.