WorldMap is a simple Android app that displays a map of the world taken from Wikimedia (http://upload.wikimedia.org/wikipedia/commons/3/33/Physical_Political_World_Map.jpg), and allows the user to scroll around on it.
The map itself is quite large (6480,3888), so it's way too big to fit in memory all at once (6480 x 3888 x 32 / 8) = 100,776,960 -- over 96 megs. The VM heap size Android supports is eith 16 or 24 megs, so we can't fit the whole thing in memory at once.
So WorldMap uses the BitmapRegionDecoder API (available as of API 10) to decode just what it needs to display.
WorldMap is open source, and the source code is here: https://github.com/johnnylambada/WorldMap