Where are all the Marvel online scans?

Sadly, you really can't. The ones you've already identified are pretty much it. You can try to find some torrent files with comics, but there are no websites that host the content straight up. The reason: Marvel is owned by Disney and DC is owned by Time-Warner, two of the biggest corporate giants in the world. They are ON TOP of making sure nobody misappropriates their stuff. It doesn't hurt that Time-Warner also controls a large part of the communication industry. There was a great website a little while ago called htmlcomics.com that hosted lots of great stuff (including X-23). Then, about a year ago the FBI literally kicked the door in, took the owner to jail and confiscated the servers. That was the end of that. They don't kid around. So, apart from the free stuff Marvel offers on its website, you'll have to resort to the old fashioned method of buying stuff.