TIP for Coursera courses.
Many of the paid courses in Coursera are literally free through the audit option. Whenever you enroll for any course check for the audit option in the dialog box which opens when you click on the enroll button. This way if you are interested in learning without the certificate then you can select the audit option and learn for free bypassing the trial option.
Lately many of the courses have been lumped into specialization which itself is not free. You need to check the individual courses of the specialization for an audit option. Coursera is making it more and more difficult to find the audit button. However, if you need a certificate you will have to pay though.