We're currently in the process of giving the Adapt online presence a revamp. As a part of this, we're aiming to set up a central online interface for Adapt plugins.
In the meantime, if you have the Adapt CLI installed, you can run
adapt search to list all plugins which have been registered with our Adapt registry.
As a short-term fix, I've started this thread for developers to list their own plugins (I've put up the core stuff already), so hopefully that will make things a bit easier :)