Originally posted by Nocturnal: Mail it to yourself (by registered mail even) and keep the unopened envelope.
Do this several times.
Do not let anyone open the envelope, ever.
Until you take your case to court, that is.
Then only allow the judge to open the envelope in open session.
Don't even let your lawyer touch it (yes, you still need one).
Just hand it to the bailiff, who will hand it to the judge.
This is the Poor Man's Copyright.
Don't leave home without it.