A stealthy startup called Flipboard has raised funding from Kleiner Perkins Caufield & Byers, we’re hearing from multiple sources.

What is Flipboard? We’re not sure. But it must be an exciting concept or team if a brand-name firm like Kleiner is willing to back it pre-launch. Kleiner has declined to comment.

There’s nothing public at flipboard.com, and the Flipboard Twitter account has a single, not particularly revealing tweet. But whatever Flipboard is, it looks like the app or site posts messages to Twitter, judging from a couple of examples floating around online. It may also be relevant that when announcing the expansion of Kleiner’s iFund for iPhone and iPad apps, partner John Doerr said the iFund has two stealth iPad companies that were about to launch.

While we were looking into the story, we also heard that there was “lunchtime chatter” that Index Ventures is another participant in the round. On its own, that doesn’t sound terribly reliable, but it’s worth including, since it corroborates our first source on the Kleiner backing, and also names a second investor. Index Ventures partners Neil Rimer declined to comment.

I’ll update this story as I hear more.