When the brouhaha about TrueCrypt started, I wrote a zsh wrapper for "mounting" GPG-encrypted tarballs as directories: https://gist.github.com/gcv/b7d72023a851f2edf951

It works well as a TrueCrypt replacement for me personally, but has a couple of warts. Secure rm is slow on cleanup, and the user needs to be careful about the hidden files it uses to keep track of volume metadata.