There are a ton of Udemy paid courses that go on discount or totally free from time to time so check regularly.
Here is a list of all free courses on Udemy.
This is indeed a bit of a difficult one as it's a commercial outfit albeit offering free stuff now and then. I'll have to see what Dave wants to do as free stuff is always good to post up as a sticky but commercial people should really be paying for an advertisement slot, that's what keeps this thing going
isn't there a list of online resources it can go in? with a note that it's mostly commercial, a whole sticky is indeed over exposure.
Just to clarify things, the Udemy free offer courses that I have seen don't expire once signed up during the free offer period. They aren't bait and switch tactics, more promotional to get people to view and review the courses and get likes etc, much like a restaurant giving free meals.
I've been using them for quite a while and never paid a cent as most of topics I'm interested in come up from time to time with a free course, some of them are quite comprehensive but don't expect an engineering degree here.