The FCC's developers page happens to have a sidebar linking to many other US government agencies' developers pages, APIs, etc. It's a handy list, but I assume the FCC hosts it only out of the goodness of their hearts (and only as time allows)---surely it's not within the FCC's scope to track this sort of thing.
Is there any other agency or office that keeps an official and/or complete list of government agency developers' pages?