If you want to transfer files to or from your iPhone at ease, check out this video on how to SSH / SFTP into your iPhone. SSH (Secure Shell) and SFTP (Secure File Transfer Protocol) all can be used to safely transfer files to your iPhone!
You need to ensure that your iPhone has already been jailbroken. If you are unsure of how to do this, search WonderHowTo for iPhone jailbreak videos. This particular iPhone is jailbroken using Cydia.