Here are two of my favourite sites about letter writing, which is a fantastic way to practise your English. However, you can’t really reply to these letters, but you do get to read them.
The first, Letters of Note, is a high-quality collection of letters by famous people. Some of the world’s greatest writers and notable public figures have letters reprinted on this site.
The second is less notable, but a lot funnier – usually in the peculiar meaning of funny rather than the humorous meaning. Passive-Aggressive Notes is an excellent way to find out how crazy people can be.