CryptSync is a small utility that synchronizes two folders while encrypting the contents in one folder. That means one of the two folders has all files unencrypted (the files you work with) and the other folder has all the files encrypted.
The synchronization works both ways: a change in one folder gets synchronized to the other folder. If a file is added or modified in the unencrypted folder, it gets encrypted. If a file is added or modified in the encrypted folder, it gets decrypted to the other folder.
This is best used together with cloud storage tools like SkyDrive, DropBox or Google Drive. If you want to use such cloud storage for backups, it's a good idea to keep your private data really private. That means only uploading encrypted files to make sure no one else can access your data. Because even if the companies behind the cloud storage guarantee your privacy, it's always possible that your account gets hacked: so make sure you use a different password to encrypt the data with CryptSync than you use to login to your cloud storage provider!
CryptSync - 64bit software