I'm still following the course at JustinGuitar.com, but I'm also constantly looking at other guitar lesson stuff.
The second stage of Justin's course is the compliment of the first stage. The first stage is the A, D, and E major chords. Stage 2 is the A, D, and E minor chords. They're very similar, but at this point hearing the difference between them is a lot of fun. Minor chords seem so sad, which isn't to say that major chords sound happy, G Major in particular sounds a lot like E Minor.
The first stage chord changes are incredibly easy, even for me. Justin't One Minute Changes exercise (which is a test to see how many times I can change from one chord to another and back again in one minute) showed me that I can actually change some chords really fast, but these minor chords are far less easy than the first three. I'm still pretty high up there, much better than someone who's just starting, but following the course through again, properly, is helping me tons.
I discovered musicisum.net recently. At least the first videos I've seen star Rabea Massaad, lead Guitarist of Dorje, band of Frontman/entrepreneur Rob Chapman. For the most part, the lessons take a gamified approach, something I don't mind. Justin's course assumes I can cut out the time on my own, and puts the onus of moving onto new stages onto my own shoulders. With a bit of experience, it's not too hard to tell when I should move on, but practicing on my own sometimes feels unproductive. Musicisum includes practice spots, where I can time myself, listen to examples of the exercise done correctly, and see how long I've practiced.
The lessons take much the same path; teach the open chords first, practice changing them, and then learn to strum. It's not different, but I really like the website and the videos are really concise. Justin can ramble a bit without making too much of a point, like a teacher might if you were to play with them, but sometimes it seems like he can say a lot without teaching anything. Rabea makes his point and moves on. Of course, Justin's videos are much older, and it seems like he did it all himself. Rabea is for sure not doing this alone. The quality feels higher, but Justin's videos aren't that far behind, they're just a little long.
Musicisum also grants some kind of instant gratification. Since it's a web app, it can list your 'achievements.' Every lesson is a badge, and getting those badges is satisfying. In the long run, this probably won't matter much. Learning guitar is its own reward, but I'm sure it can help beginners out there to get started.