Are Visiting Assistant Professor salaries negotiable? I have two offers for a Visiting Assistant Professor position. Can I negotiate for a higher salary for a VAP position?
You can certainly try to politely negotiate salary, but I wouldn't count on getting much if anything at all.  

At my institution, my experience has been that the administration simply won't negotiate on salary.  For a VAP, the department is simply looking for someone who can handle teaching load for a year or two.  There are typically many qualified applicants with enough teaching experience, and because the position is temporary there just isn't any point in paying more than necessary.