Participating in this forum has helped me much more than any specific class I have ever taken.
This is less true for me, not due to any deficiencies or shortcomings with ET but because I'm not an engineer and never went to university, and as such find often enough that posts in the eighteen fora here that I lurk in are frequently over my head, meaning I am literally out of my depth, so I just don't get involved in those...but for those where I do weigh in, I thank you for your continued sufferance of my presence.
Beyond that, this forum, Generator and Motor Control Engineering, and the Electrical Engineering General Discussion fora are where I am most comfortable, with the boiler and thermodynamics ones not far behind.
I'm very appreciative that over the years my employer has seen fit to send me on and/or has brought in instructors to provide myself and my colleagues with training on such topics as supervisory skills, instructional techniques, NERC certification, propane handling, speed governor operation, power system restoration, relaying, and numerous others; these have proven of great value. I should add that the union that represents me had to fight, sometimes hard, to get training time built right into our schedule - but the impressive results became obvious in relatively short order, and the company soon chose of its own accord to increase the percentage of our working hours allotted to training; in all fairness I must offer kudos to them for recognizing the returns the investment paid, and I definitely commiserate with those of you whose employers "don't like you not working," which I have by personal experience come to see as a very short-sighted view.
On a more personal level, I have found the Canadian Power Squadron's Basic Boating course I took years ago to have stood me in good stead in quite a different number of situations.
CR
"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]