I recently discovered a wonderful new blog called "Letters of Note" which showcases interesting pieces of correspondence. A thank-you letter from Tolkien to a fan was posted there today:
http://www.lettersofnote.com/2009/11...htful-one.html
Though hardly Tolkien's most intriguing letter, it is a delightfully warm and generous response to a fan, and it's
so characteristic of Tolkien that even in such a short note he spends the better part of one page (of two) speculating on the origin of Miss Honeybourne's name.
Be prepared to lose an hour perusing the site...