How to Write an NIH Grant Application is an article at the AAAS's GrantsNet site that provides links to a number of sites with information on preparing grants for the NIH.

Ten ways to write a better grant

Writing and Research: On-Line Resources is a helpful article for graduate students.

For information while your writing, www.bartleby.com is an online publisher of reference books. The site includes an encyclopedia, dictionary, thesaurus, and a number of style guides. Very helpful for any grammar or spelling questions you might have.