Great suggestions in this thread. I'd also add:

There's a good excel logbook template in the downloads section of this web site. Save the file in Dropbox so it's automatically backed up "in the cloud". It's not Logbook Pro, but the price is right.

In addition to keeping the old logbook in a safe place, I also xeroxed it and keep a copy at my parents house. That way I have a paper backup in a remote location.