Which is why I wanted to mention two websites that keep up with those online magazines so I don't have to. The first is one I've just heard about -- Fiction Daily. Fiction Daily (which looks suspiciously like Andrew's Book Club) is an aggregator, of sorts:
It’s hard to know where to go, what to read, or why. FictionDaily’s goal is to help aggregate and organize this sea of new literature. We try to make it accessible to readers who want to see what literature is up to. We aim to help others find the pulse of literature.In addition to snippets of new stories in online magazines, with links, Fiction Daily includes a list of links to a lot of online resources, including magazines.
The second one is something I've mentioned before: Five Star Literary Stories. Five Star invites the editors of online magazines to nominate a story and then finds a reviewer for that story, giving exposure to the magazine, the author, and the reviewer all at the same time. Very nice.
There are no doubt other sites that help promote online literature. I'd love to hear from readers if you know of others.