this effect is actually fairly easy to accomplish. there are several ways you can approach it, of course.
i think i have actaully written directions/tutorial on this for someone recently , as i have these 2 examples built and can't remember why:
ww.demetri-media.com/FlashTalker/SliderScroll.swf and
ww.demetri-media.com/FlashTalker/SliderMenu.swf
they are both built using greensock's excellent tween engine, TweenLite:
http://www.greensock.com/tweenlite/
i will look for my write up on them if i can, but basically it is just a long horizontal movieclip symbol, that has other movieclip symbols nested inside of it to act as the 'buttons'.
the parent clip ( the long horizontal movieclip) is on the main stage and is masked out to just reveal however much you want to show.
back and forward buttons are scripted with event listeners - mouse over or clicks, whichever you want. thier functions use TweenLite to move their X position.
the nested movieclips( those acting as 'buttons' ) are further scripted if wanted to perform a function ( navigation, etc )
that's really all there is to it. hope that gives you things to think about.