This is a collection of links to answers to those questions, mostly maintained by other people.
Celebrities have as much, or more, reason than most people to keep their e-mail addresses private.
There are penpal clubs, but I haven't researched them yet. You could find a newsgroup about a subject in which you're interested, read it for a few weeks, then see if someone who posts there might be interested in correspondence. This list hasn't been updated since 1996, so is likely out of date. Don't, unless you want to become known as a spammer. For other forms of copying, contact the current maintainer.