For years Robert Jordan has commented on another series of books he's been planning. We finally have something concrete. From the April 2005 issue of Locus magazine we learned the following:

ROBERT JORDAN sold the first three books in his new Infinity of Heaven series, "high fantasy with a touch of Shogun," to Tom Doherty at Tor.

Update

Robert Jordan's next fantasy series, entitlted INFINITY OF HEAVEN, will (as of right now) be 6 books long. He will finish THE WHEEL OF TIME before focusing on this new world.

Dragonmount was able to talk to Robert Jordan and get some preliminary info:

DRAGONMOUNT: Is this the "Shipwrecked" series you've been referring to for a while?

RJ: Yes, this is the "Shipwrecked" series, although what I originally thought of as the first volume actually turned out to be the second.

DM: Will you write this before or after you finish the WoT prequels?

RJ: Infinity of Heaven almost certainly will be written before the prequels, though I might do them between the Infinity books. 

You know, the reception of New Spring: the Novel surprised me.  Some people were upset or even angry that I wasn't getting on with the main story.  I even heard people say there was no reason to read the novel if you had read the novella.  (That, by the way, is very wrong.  There is stuff in that novel that won't ever be anywhere else, including the test for Aes Sedai and the reasons why certain people have the relationships they do in the books among other things.)  Anyway, given the reactions of so many people, I decided to shelve the other two prequels for a while.

DM: Any clues to what the title of the series means?

RJ: RAFO.  Heh-heh.  You didn't think I was going to abandon that, did you?

DM: How many books will there be in this series? (I mean... REALLY...how many? heh heh)

RJ: The plan is for two sets of three books each, much more tightly focused.  In many ways, The Wheel of Time is a story of nations and cultures undergoing change as much as it is a story of Rand or Mat or anyone else.  I still intend to take you to a very different world -- in some ways MUCH more different than the world of WoT -- but I won't have quite so many story lines running.

Yes, I think it's pretty exciting, too.  This thing has been bubbling around in the back of my head since about 91 or 92, so it has had a good long gestation.  And more to come, since I haven't finished Wheel yet, and I'm certainly not going to do any work on Infinity until I do.

As more information becomes available, you'll find it here on DM.