What good widely available courses (e.g. textbooks, online classes) are there for people who wish to learn (or continue to learn) Latin on their own? What are their benefits and drawbacks?
Please give only one course per answer. If you have many courses to suggest, give multiple answers—but read the other answers to avoid duplicating answers. This way people can vote on individual courses, causing the best ones to rise up and the worst ones to sink down, so that we can easily find the most loved courses. If there are many courses listed in an answer, it's hard to link the answer score to the quality of each listed course.
Note about resource questions:
Broad resource questions like this are generally not allowed on this site. The community chooses a select few to avoid an overflow of questions of this kind. If you have an opinion on what resource questions should be asked next, post a suggestion in this meta post or vote on the existing ones. The ones to be asked will be chosen from that list according to their number of votes. If you have ideas about listing resources on this site in general, you can contribute to this meta discussion.
In particular, if you would like to ask a similar resource request question, do not just ask it, but post a suggestion in the mentioned meta post instead.