I don't usually plug people or products, but this one I have to. Since reading this dudes book (and attending a few seminars) every manuscript I've submitted has been given a comment or two or three (depending on the number of reviewers) along the lines of "This is an easy read."

The book: Expectations: Teaching Writing from the Reader's Perspective
The author: George D. Gopen, Professor of Rhetoric, Duke University

Here is an article (online, PDF) of his that appeared in the American Scientist.
http://swerl.tudelft.nl/twiki/pub/Main/ResearchAssignment/Science_of_scientific_writing.pdf

You can thank me later.

No prob. Your library could probably get it through interlibrary loan if you didn't want to drop the 60+ ducats on the book. I can't tell you how many times in graduate school I copied entire books on our labs photocopier from the library. I still have my copy of Intuitive Biostatistics on my shelf here at work.