Planar enthusiasts might be pleased to hear (if they haven't already) that the next Open Design project is going to deal with the multiverse (if enough patrons are found): http://www.koboldquarterly.com/k/front-page9819.php
Dark Roads and Golden Hells is near full funding. The official announcement is expected early next week, likely during GenCon. If planar adventures in the style of Planescape is something you are interested in, have a look at the project and see if it is something you might like to support and participate in the development.
Believe me, I would've offered my contributory support for such a project the moment it was announced, if only I had the time.
To revisit what made PLANESCAPE one of my all-time favourite worlds, and in a product for the ODP no less, has been something I've been waiting for. But the increasing pull of the black hole-like gravity-well of my ever-expanding "To-Do" list makes significant demands of what little free-time I have.