Library Online 
Offers a selection of prewritten customizable letters.
http://www.libraryonline.comLetterWhiz
Offers a multitude of professionally written, fully customizable letter templates for all occasions.
http://www.letterwhiz.com/
Business Letter Templates
Sample business letters available for download with subscription.
http://www.business-letter-templates.com/
Writing Professional RFP Letters
Templates and samples: RFP cover letter, letter of intent, rejection letter, disqualification letter, decline a proposal, protest against unfair contract award.
http://www.rfp-templates.com/
