This letter simply thanks someone for doing something thoughtful.
1234, Main Street
Boston, MA 02123
07 April, 2005
<Recipient Address Goes Here>
How can I ever thank you enough for your recent thoughtfulness? It was so kind of you to <what person did>. It was just what I needed! You always seem to know the perfect thing to say or do. I am truly touched by your generosity of spirit and willingness to go out of your way for me. You are a true friend and I am indeed thankful to have you in my life. Thank you again for always being so thoughtful.
encl: <List of enclosed items goes here>