In September, Coursera will once again be offering an 8-week course on science writing. From the Coursera website:
This course trains scientists to become more effective, efficient, and confident writers. This is a hands-on course that emphasizes interactive examples and practice. In the first four weeks, we will review principles of effective writing, examples of good and bad writing, and tips for making the writing process easier. In the second four weeks, we will examine issues specific to scientific writing, including: authorship, peer review, the format of an original manuscript, and communicating science for lay audiences. Students will complete editing exercises, write two short papers, and edit each others’ work. The primary audience is undergraduate science majors, graduate students in scientific disciplines, and professional scientists. Students from non-science disciplines can also benefit from the training provided in the first four weeks (on general principles of effective writing).
Best of all, it's free! It begins September 24 but you can sign up now.