Email has pretty much taken over from letter writing theses days. Which is a bit of a shame really as there's nothing quite like the feeling of receiving and opening personal mail.
In the same way that email has taken the place of the letter so too has the email signature taken the place of the letterhead. Which is another great shame as a great letterhead beats a dodgy old email signature hands down.
To see for yourself how good a letterhead can be click here and go see some genuine classics.