I would have started new research projects, especially coauthored ones with colleagues and faculty. Of course JMP and dissertation chapters should take precedence so maybe this isn't an option, but I felt I missed out on so many good ideas the summer before the job market. I kept saying, No, can't start anything new, must polish and polish app material, which can be so mind-numbing and demoralizing. This is going to be the last summer in your department (hopefully), and it will likely be difficult to work on and start research with most of the individuals you currently interact with. Not to mention, having ideas and projects started can be a huge save during interviews. Several times I felt the interview team was bored with my JMP and papers and it would have been nice to have some developing ideas to also discuss with them (even if they were not on your CV).