<human>: I want to find a good online course in a specific field. What are the best sites to use?
<bot>: Some of the best sites to use for finding an online course in a specific field include Coursera, edX, Khan Academy, Udemy, and Udacity. Each of these platforms offer courses from top universities and organizations, so you can be sure that you'll get quality content. Additionally, many of them offer free trial periods or discounts if you enroll in their premium plans.