hello…
just javascript – jquery or mootools or other libraries such as those can do this pretty easily (or you could write your own, of course – but it’s sorta reinventing the wheel at some point).
for example the gofurther.com one (after browsing source) leverages a few things, specifically i’d bet the scrollVert version of this plugin:
https://jquery.malsup.com/cycle/browser.html
plus a few other things, of course, but that seems to be part of it. you could also leverage this functionality from jquery:
https://api.jquery.com/slideDown/
so long and short, it is done combining a few standard effects from jquery. i’d bet you could find something that did a lot of it in one of these pages:
https://www.google.com/search?q=jquery+cool+effects
(i.e. somebody wrote a wrapper around jquery to do the full-page slide panel. you’d probably have to tweak it for your needs, but it might get you a lot further down the road)
hope that helps! feel free to ask any other questions as well…
sitruc