Orkut will employ a directory of Opensocial Applications that will allow developer submissions.
This was confirmed by Arne this afternoon.
(02/05/08) Update: Google's Orkut Application Directory submission form was recently made available. We highly recommend NOT rushing your submission, instead, make sure you have everything in order before you submit.
It appears that each container will be handling it's own Opensocial application directory, but we anticipate that the Opensocial team will develop a submission standard so that container-specific directory submissions won't be required.
(02/05/08) Update: It's looking like network-specific directories may be all we get. We'll have to wait and see.
Google's What's up with Opensocial page indicates that: "As the number of containers grow, we want to minimize the amount of effort application developers need to use to register their apps on each container". (So no need to panic.)
The Orkut Sandbox currently contains a directory 'Teaser' that contains (6) sample applications with click to add functionality, however, developer submissions are currently not allowed.
Also, don't forget that Ning does have it's Gadget Directory online and functioning.
Developers can and should submit their completed apps that run on Ning, and Ning users can browse and use gadgets from Ning's Opensocial Application Directory.
Orkut's Opensocial Application Directory 'teaser':
Orkut's current Opensocial Directory 'Teaser' is shown below. You can access this directory from the sandbox by clicking on Applications -> Browse the Application Directory.