Sublime text has this file at a glance feature, where you see the whole file in miniature.
minimap looks like it is what you're after.
From the README:
This file is an implementation of a minimap sidebar, i.e., a smaller display of the current buffer on the left side. It highlights the currently shown region and updates its position automatically. You can navigate in the minibar by dragging the active region with the mouse, which will scroll the corresponding edit buffer. Additionally, you can overlay information from the tags gathered by CEDET's semantic analyzer.
Simply use M-x minimap-mode to toggle activation of the minimap. Use 'M-x customize-group RET minimap RET' to adapt minimap to your needs.
It lets you "thumbify" frames - regardless of what they're showing (a single file, multiple buffers, whatever). The result is a thumbnail size , fully functional frame (scroll-bar, whatever).
You can customize the size, and you define which frame parameters to use (e.g., menu-bar and tool-bar are removed, by default). At the touch of a key (I use
C-z) use can thumbify and dethumbify a frame.