Diligence and responsibility are very biblical goals to have for our children (just read Proverbs), but every parent knows how difficult it is to teach kids to work. Children Who Do Too Little (by Patricia Sprinkle) is an excellent book that will stir you (and disturb you) about the importance of teaching your children to do "chores" and to have an overall good work ethic. 

You'll want to have a highlighter handy as you go through this book! The author suggests jobs for different age groups; she also offers practical tips for motivating and incentivizing hard work. This is a wonderful resource to be read and re-read whenever you feel like throwing up your hands and deciding it's too much work to get your kids to work.