Natalie Goldberg's Writing Down the Bones is a terrific book for writers and poets, whether they are in need of inspiration or not.
Writing Down the Bones is a collection of essays on what it means to be a 'writer', ideas for jump-starting your creativity, workshop-type exercises for the uninspired, and supportive guidance for the unmotivated.
For example, the chapter titled "Composting" helps writers to realize that although they may be going through an unproductive period, ideas and experiences can and are being 'composted' for later use. The chapter "Doubt is Torture" talks about the negative arguments writers use to discourage themselves from writing, and how they can break free of the doubt.
Writing Down the Bones mixes personal vignettes, helpful hints, and a dose of zen dogma to provide a humorous how-to for both the novice and experienced writer. While much of the advice is common sense, Goldberg manages to present it in a fresh way.
This book should be on the shelves of every writer. If you know a writer who's going through a slow period, buy one for them as well. Maybe they'll even thank you -- in writing!