We have a profile question on membership sign-up at the Raleigh Durham Web Design Meetup, that asks for member's favorite reference and tutorial sites.
Last year I sorted and ranked the top links from several hundred member profiles and came up with this list:
Perhaps some of these are way off-base from your question, but a few, especially the Wordpress-based sites (smashingmagazine, alistapart, and net.tutsplus) are quite visually interesting. The original posting is here., and contains the runner-ups and honorable mentions too.
These seem to be more reference than online training. It's a nice list though. I'm happy to see that w3schools is at the top. There may be better specific references out there, but w3schools is a solid general reference.
Right in the middle of that list is the way-awesome net.tutsplus.com. I vote for that as a great example of high quality user contributed (but curated) content. If you haven't explored their site, notice they have vector software, PhotoShop, basic web design, and other areas of specialization.