After Holiday Let-Down

So, now that the holidays are over, it's time to get "back to reality". I will be finishing up my first Science Fair in the next month. This has been an experience I have enjoyed however, it has become rather bothersom at the same time. It is at times difficult to motivate the students. In my class (7th and 8th graders) we have been working on Science Fair since before Thanksgiving. They have had ample opportunity to complete all of their research, type all of their papers, etc. in class. I have made deadlines, given timelines, used sciencebuddies.com as a guide and still have kids who slack off. How do you deal with these types of situations? Am I just expecting too much? How do you motivate your students? How do you get them excited about the subject?