"Issuu is the place for online publications: Magazines, catalogs, documents, and stuff you'd normally find on print. It's the place where YOU become the publisher: Upload a document, it's fast, easy, and totally FREE. Find and comment on thousands of great publications. Join a living library, where anyone finds publications about anything and share them with friends."
I was introduced to this site thanks to Keyhole, who has put their first two issues on the site. It looks just like the magazine, and as you view it, you can see the pages visibly turning. You can also "rate" publications and leave feedback, among other networking features.
It's fun, easy to upload and use (except search categories are a bit limited right now - a lot getting glommed into a few categories). Good for mags to keep the print "look and feel" - even online. Also good for mags that run out of issues before the next one is out.
Downside? Searchability of content using tools like Google. Might be able to find the publication itself, but not content - ? It would be a good duplicate resource for readers, but probably best to keep key searchables (like author names) on individual sites.