At Guitar Strings For Life, you can get "free" guitar strings. They're actually $2.98 "shipping and handling," but not a bad price. I've purchased two sets. Unfortunately, I haven't had a need to use them yet and so I can't review them. But I'm a cheap strings kinda guy, and I expect that they'll be perfectly good cheap strings. They also run a raffle that you can enter once a day. The drawing is every few months. The prize is a $100 (IIRC) Guitar Center gift card.
Udemy is an online course provider. They're running a $9.99 "Black Friday" type sale right now. Once you've purchased a course, the materials (video lectures, audio, PDF lesson files, etc.) are available for life. I've taken two courses (one on guitar, one on harmonica). Haven't completely finished either one, but I've learned quite a bit from both and am planning to take more once I finish these. Not just music, either. Pretty much anything you might want to learn about.