I've seen mention somewhere on these forums of a book being published in the near future that deals directly with planar stuff. (Smells like planescape to me!)
Anyone know the dark on this, or have a link handy?
I suspect that the malhavo book will be more planescape than the WotC one. An that the SL one will be fantastic for SL, and only mildly interesting for the rest of us.
Also, there is Portals and Planes, from FFG and Enkwell has a planar adventure which takes place primarily on Gehenna. It is called The Love of Art: Drawn to Gehenna -details can be found here:
Further, keep an eye out at Enkwell for more planar-related releases, as we just Interlinked with Green Ronin on the Book of Fiends (also a planar book) and will be putting out some additional/support products for it!