The WoW Armory website used to be written in XSLT on top of a horrendeous java stack. It's commonly referred to as the badmory and was slow as all hells. It had a pure-html fallback (rendered serverside into html) for unsupported browsers. It's one of the worst pieces of web I've ever seen... and I've seen some stuff.
It's no longer using all this, of course. They hired the guys from wowhead.com and had them redo the whole thing in a saner stack.
An interesting example I came across is documenting an xml schema by converting it to xhtml. I think it goes without saying that Javascript and JSON make react a lot friendlier though.
