DISCLAIMER: I've spent an hour to visualize a large Makefile I needed. So, sorry if it won't work for you.
makefile2dot has been written to visualize Makefiles, e.g. GNU make Makefile. It is written in Python and implies that you have Python and GraphViz "dot" utility installed:
sudo apt-get install graphviz python
python makefile2dot <Makefile >out.dot
or
python makefile2dot <Makefile |dot -Tpng > out.png
This example Makefile will result in this png-image:
