I recently found a site with an extensive list of FREE Business Letters. The site is named, 4hb.com which in my opinion is a pretty useless name but they have over 580 forms and letters you can use.

Their letters and forms are listed in alphabetical order and here are the first 20 of their current collection of nearly 600 entries

   10-Day Notice Before Collections on Delinquent Account
   30-Day Notice to Quit
   Acceptance of Counter Proposal
   Acceptance of Order With Delivery in Lots
   Acceptance of Purchase Security Agreement
   Acceptance of Resignation
   Acknowledged Receipt of Goods
   Acknowledged Resignation
   Acknowledgement and Acceptance of Order
   Acknowledgement from Publisher, Comments Referred to Author
   Acknowledgement of Application
   Acknowledgement of Cancellation of Backorder
   Acknowledgement of Change in Meeting Date
   Acknowledgement of Customer Praise of Employee
   Acknowledgement of Letter
   Acknowledgement of Merchandise Returned for Repair
   Acknowledgement of Modified Terms
   Acknowledgement of Notification of Lease Transfer
   Acknowledgement of Receipt (Documents)
   Acknowledgement of Receipt of Estimate

You can find their home page at: 4bh.com

They also have many good articles on general business issues on their: Library page. They devide their Library into eight sections:

Start and Run a Business, Communicate, Diversions, E-commerce and the Internet, Sales and Marketing, Money Matters, Home Office and Wisdom and Life Skills.

I didn't even try to figure out how many articles are in their Library altogether but in just one of these sections, their Home Office page, they feature these articles:

   Good Fences Make Good Neighbors in Business and Life
   Start The New Year With A Fresh Perspective
   How to succeed as a stay-at-home Parent
   Data Loss... Can Your Company Survive. (Most Do Not)
   Think You Can’t Afford the Help You Need? Think Again!
   Organization Tips That Add More Hours To Your Day
   Finding Motivation: What To Do When You Don't Feel Like Doing Anything
   Get Things Done! A simple guide to getting on top of your life and having some fun!
   Better Business Bureau - Tips on Work-At-Home Schemes and Scams
   Your Home Office - Stay Put or Move Out
   Your Home Office - Top things to make your office at home succeed
   How To Succeed Working at Home
   Creating a Corporate Image from your Spare Bedroom
   Putting Theory into Practice. . . A Personal Perspective
   Providing Better Customer Service - Home based Basics
   Break Time! - Home based Basics
   Considerations for Becoming Self-Employed - Home based Basics
   Working from Home - Judge our Quality not our Location - Home based Basics
   Start up Business - Home based Basics
   Home based Basics - Stay Home or Move Out? The "Rules" defined...
   What To Wear When You Work From Home

So, if you're looking for a great source of free, professional quality business letters and forms and articles, 4bh.com is the place to start your search.