I have developed some python scripts available here. I have used them in EE705 (VHDL, verilog) and found them very useful. It generates detailed log (which file matches which file) and sent emails to offenders with an archive of all file which were matched. It is integrated with my moodle-application (automatic download, extract, compare, sending-emails.)
It also generates graphs (using python graph-tool) which shows the level of copying in the assignments. Few graphs are attached in this post.
Thickness of edge (and hotness of edge color) shows the level of similarity. This gives a quite a picture of the class.