Encrypting files with openssl for synchronization across the Internet
Well, shortly after I wrote about encrypting files with a keyfile / passphrase with gpg people asked about a solution with openssl.
You should prefer to use the gpg version linked above, but if you can't, below is a script offering the same functionality with openssl.
You basically call crypt_openssl <file> [<files...>] to encrypt file to file.aes using the same keyfile as used in the gpg script (~/.gnupg/mykey001 per default).
A simple crypt_openssl -d <file.aes> [<files.aes...>] will restore the original files from the encrypted AES256 version that you can safely transfer over the Internet even using insecure channels.
Please note that you should feed compressed data to crypt_openssl whenever you can. So use preferably use it on .zip or .tar.gz files.