I stumbled upon Letters of Note yesterday and it is a fascinating site. according to the site its goal is:
Letters of Note is an attempt to gather and sort fascinating letters, postcards, telegrams, faxes, and memos. Scans/photos where possible
The site has great examples of well crafted letters by people that have played roles of varying importance in society. These letters are wonderful little glimpses into the lives and thoughts of people we have all read about.