Blow are the absolute best business writing websites and resources out there. They have tips on everything business-writing related including language, tone, etiquette, memo writing, and proofreading. All of these resources are worth book-marking in your favorites or printing out for future reference:
Online Writing Lab: Abbreviated OWL, this website is the godfather of business writing and etiquette. It includes hundreds of resources on business writing including business letters, memo writing, email etiquette, language and tone guides, proofreading, and revision, all in accessible handout form.
Brief Guide to Business Writing: This is a great printable booklet on the basics of business writing put together by the Department of Management and Organization at the University of Iowa. It outlines all there is to know about business writing and includes samples of emails, memos, and business letters.
WikiBooks Business Writing: Take the wiki approach to business writing with this useful open-book site. Start here to explore all there is to know about business writing.
Colorado State University: Perfecting you business writing can be a long and sometimes daunting process. Learn how to craft your writing from start to finish with this writing guide that covers the essentials of conducting research, planning, drafting, organizing, and revising.
Research and Documentation Online: Another excellent resource for formatting and structure, the Research and Documentation Online website allows you to choose a discipline (such as business) and what you need assistance on (such as formatting). It will then provide you with a user-friendly reference page to answer your questions as you work on your paper.
Online Technical Writing: This is one of the best places on the web for anyone in business communication. The guide highlights all aspects of business writing including reports, memos and letters, as well as document design, processes and guidelines to help you from start to finish.
Keep in mind that the road to consistently successful business writing is a long one. These resources will help you along the way but ultimately it's up to you to work on improving your writing skills. Take your time, always double- and triple-check your work, and aim to be clear and concise. And remember, if you get stuck along the way, there are 100 helpful websites just a click away. Good luck and have fun!
Further help can be obtained via a number of different methods: