Sounds like what you're looking for are shared world series. Here's a few off the top of my head, not all of which are fantasy:
Thieves' World -- edited by Lynn Abbey, but be aware these are short story collections. All of the authors submitting stories are working with the same setting, though
Dungeons & Dragons -- they put out a LOT of fiction, and there's a lot of authors
Battletech -- not fantasy, unless you argue that mecha taller than a suburban house is getting into the realm of the fantastical
Star Trek -- again, not fantasy per se
Some libraries put shared world fiction all together in one location on the SF/F shelves, others (like my nearest one) don't. Not all libraries are created equal, either -- if you're in a large urban or metropolitan area, I'd say your odds are better for finding a variety of series and authors. Take a look.
Otherwise, head to your nearest large bookstore and see what's on their shelves. I think it's standard for them to place the multiauthor series/shared world fiction clumped together next to the rest of the SF/F.
