Book Crossing for beginners

I first came across Book Crossing via a friend some years ago but have recently rediscovered its merits.  The premise is that you leave a book in a public place for someone else to find and read.  Each book that you 'send' out into the world on its travels has a unique code that you log on the Book Crossing site.  The person that finds the book then records it, reads it and leaves it somewhere else for someone else to find.  The book can be tracked on all its travels as long as people who find it remember to log on.  It's such a fantastic idea.  Apart from the thrill of seeing where your book has ended up, it's a great way to share books that you no longer want or need; So now I can see a way to get rid of all these...

So, what will my first book be and where shall I leave it I wonder?  Has anyone else done this and if so, what was the furthest that your book travelled?