1. A Dictionary

Spell check is great, but you still need a good dictionary. It will include many words that spell check won't and the definitions will help you determine if you are using the right word.

Merriam Webster's Collegiate Dictionary. A good, solid choice for the office setting. You can also get a CD and online access, which makes looking up words extremely easy.

2. A Thesaurus

When you are searching for the perfect word that says what you really mean, you need a thesaurus. It's also the tool you need if you find yourself using the same words over and over.

Roget's Super Thesaurus. This reference includes not only synonyms, but slang, quotations, and common phrases associated with each word.

3. A Grammar Guide

Grammar guides will answer lots of pesky writing questions for you. If it's something you think you were taught in high school English, but can't remember it now, check a grammar guide.

Woe Is I. Not the least bit stodgy (like so many grammar guides out there), this guide is very easy to use and includes lots of humorous examples to illustrate its points.

4. A Style Guide

While many grammar questions are black and white, a style guide helps you make all those writing decisions in the shades of gray. Most people base their editorial style on one of the three guides below.

The Chicago Manual of Style. This style guide is considered the more formal of the three here and is especially popular with academics, technical organizations, and book publishers.

Associated Press Stylebook and Briefing on Media Law. The AP Style Guide is easier to use than the Chicago Manual of Style. It works well for organizations that publish content more along the lines of what you'd see in newspapers and magazines.

Gregg Reference Manual. This is considered a business writer's style manual and is probably the easiest of the three to use.

5. A Writing Guide

Writing guides do what all of the references above cannot: teach you how to write well. If you have trouble conceptualizing your message, organizing your thoughts, and putting them to paper so they make sense not only to you, but to your readers, you need a writing guide. The guides below will be useful even for people who consider themselves skilled writers.

Words Fail Me. Serious advice in a light-hearted, easy-to-read, casual tone.

On Writing Well. Lots of practical, no-frills advice on how to write with clarity, simplicity, and strength.