As a teacher, how can you deal with a lack of parental involvement?

I definitely understand your concern.  I would like to make a small point about parental involvement.  Parental involvement is a double-edged sword.  While it can be great to have, it can also be a source of frustration.  Parental involvement could lead to dozens and dozens of parents or families trying to micromanage you, your classroom, and your students.  That could be detrimental to the classroom environment that you are trying to create.  

So, what to do about a lack of parental involvement?  There are two choices in my opinion, and they are polar opposites of each other.  The first is to do nothing and make the best of it.  Your students are your priority.  A teacher could spend a large amount of time trying to get parents involved and have little to no success.  The problem is that the time spent on the parents takes away from time that could have been spent on students and class time.  

If a teacher wants to get parents more involved, though, there is a variety of things that a teacher could try to do.  Personal phone calls home once per semester is one thing that I do.  I make sure that every family of a student that I teach gets a phone call from me.  And for that phone call, no matter what, I make it a positive phone call.  I tell the parents something good about having their child in my class.  Email works too, but it doesn't work as well as a phone call.  Everybody gets email these days.  It's more rare to get a phone call.  A colleague of mine foregoes the phone call and sends a hand written card to each family.  She gets great feedback about those.  Think about it.  How often do people get real letters in the mail anymore? 

You could design homework assignments that require a small bit of parental involvement.  My masters thesis was on this very topic, and the research suggests that those types of homework assignments improve student learning as well.  For example, in a business math class, a part of an assignment might be to ask their parents how they use the current class topic in their weekly life.  

Another way to perhaps increase parental involvement would be to host an open house.  It's best done on the school level, but you could make it work within a single classroom.  Tie it in with some kind of project that the students complete.  My school's art teacher does this once per semester.  She hosts a student art show near the end of the semester, and parents come to see the work that their child has done during the course.