A long time ago, in a galaxy far far away, I did something similar. I wrote the letter and mailed it out. I only got one response, but it resulted in a great relationship - I flew part-time for the company for 5 years. After I left to move on to greener pastures, I got phone calls and inquiries from them for nearly 3 years making sure that I was happy at my new job and offering me a position full-time if I ever wanted to move back. Don't expect the whole world to come knocking at your door; but remember, all it takes is one.
'Sled