I recently started to play around with a useful tool called TrueCrypt. It allows to create an encrypted diskfile, that can be mounted on most major operating systems by giving the proper password.
This comes in REALLY handy, when you have a USB key chain drive to spare: I have been using it to store a lot of my personal information like passport and credit card numbers, but also scans of certificates, degrees etc.
Given the fact that you can employ a triple encryption using AES, Twofish and Serpent, along with RIPEMD-160 or Whirlpool for hashing. The code is open source.