Are there any? I mean obviously there used to be the SpaceOrb 360, but is there any modern equivalent? I'm thinking using the 3DConnexion SpaceNavigator, but it'd be awesome if there was a dedicated 6 Degree of Freedom gaming controller.

After learning that 3dconnexion SpacePilots were selling for just under US$64 shipped on eBay in the Independence War subforum, I got one myself.
Pretty nice device. Certainly lacks the center play of my SpaceOrb 360-nice, tight response and feel to it. Of course, you'll have to use GlovePIE and PPJoy in conjunction with 3DxWare to use it in games. (DCS: Black Shark is a notable exception, however...but it's not a title for which I bought the device to begin with.)
(And speaking of the ol' SpaceOrb, I think I'm going to pawn mine off now that I have the SpacePilot. Problem is, cosmetics aren't the best, but it does work. I'd even throw in a full Descent II CD with it. Who would buy these things nowadays, with no Vista/Win7/64-bit drivers?)