Most of the MOOCs have moved to some version of paid courses, yet most of them you can still access some free courses.
- Coursera - they have moved to mainly a free trial → paid
- edX - they still have free courses, but you have to pay for a certificate
- Udacity - they still have some free courses, but have mainly moved to paid courses
At Free Online Courses - Advance your Career you can search through an aggregated course catalog, and you filter by free courses and also see if they offer a certificate or not.
Hope this helps some!