In Pharo, I've created an infinite desktop a la Self. To make things manageable, I'm currently writing a RadarView (also just like Self) to show a map of all the objects on the desktop, and the position of the current viewport.
See github.com/seandenigris/LivingCode for documentation.
There is now only 1 major bug, and 3 little glitches:
1. (BUG): Every once in a while (can't figure out how to reproduce), it displays the Red X of Death
2. When the container window is moved, the contents temporarily jump out of the radar screen
3. when the radar is dragged over another morph in the Self World, the clipping gets very weird
4. One side of the blue highlight rectangle sometimes disappears on resize
#2, #3, and #4 can be seen in this screencast.