One of the best ways to get students interested in writing is to give them something interesting to write about. And, for my money, the most interesting part of the curriculum in school is science.
I got the micrsoscope out today, as I will for the next two weeks or so, so that we can have a close up look at things and then write about them in the writing center. Today Table 1 got to launch inaugurate this center. They were fascinated by what they saw. Here's a picture of their writing, too.