If you really want your data safe from prying eyes, you need a program like BCArchive. Not only does it offer Rijndael (AES), Blowfish-256, Blowfish-448, IDEA, CAST5, GOST 28147-89, Triple DES SHA-256, SHA-1, MD5 and RIPEMD-160 password encryption, it offers the more secure public/secret key pairs (PGP) with RSA, ElGamal / Diffie-Hellman, PKCS #12, X.509 formats and more.
In my hands-on evaluation, BCArchive worked well. The interface is similar enough to WinZip and WinRAR's that it should be easy for anyone with any experience at all to use. Actually, there are actually so few options (about the only thing unique is a PGP key manager) that even neophytes should be up to speed in a jiffy. I do have one or two notes/complaints. The program should react to a drag and drop action by automatically offering to create a new archive. As it stands now, you must explicitly define a new one before adding files. Also, while moving the mouse around on the create dialog to create random seeds is fun at first, it gets a bit old as time goes by.
Because of its heavy-duty compression algorithms, BCArchive obviously isn't going to be compatible with other archive programs. However, it will create self-extracting archives so the recipient doesn't have to download BCArchive. They'll only have to know the password or secret key.
I won't be ditching WinZip or WinRAR anytime soon, since they have so many features and don't force security on you when it's unnecessary--which is majority of the time for me. But I do know that the research and evidence for my next governmental corruption expose (which will be my first) will be stored using BCArchive.
--Jon L. Jacobi