You might also want to give a look to some non-government developer pages too. One of my favorites is
this one (offering continuous docs gps on the left and language selection for code samples on the right). Balanced Payments offers continuous docs gps on the left and a different sort of language selector (but also a version selector). Dwolla's very pretty documentation
does the same with a sightly different selector (and here's their write-up on
the redesign of their developer portal). RIDB (from the USDA) is another that, like the ones I just mentioned, are largely takes on
Slate, which was open sourced by Trip It. I like the fact that RIDB has an
issue tracker, though it's not integrated into the Slate-esque UI of the main docs. Here's an
old Parse blog about developer docs. I like
Shapeshift's inclusion of video. Checkr used to have chat capability built right into
its portal (chat with a developer evangelist). I also like how
Yammer features partners (could just as easily highlight consuming apps).
Hope this is helpful.