FTP (File Transfer Protocol) clients are used to move vast amounts of data locally and remotely from server to server by dragging and dropping files and folders. FTP programs were created to make moving information easier and faster rather than uploading single files at a time.
Most FTP clients are free and require little energy to install and operate. Five very free, very simple, and well-made FTP clients are FlieZilla, CyberDuck, Core, Coffee Cup, and Free FTP.
FileZilla works with almost any operating system (Windows, Mac, Linux, etc) and offers almost any transfer method you could want! With a variety of features such as pause of upload, remote file search, tab-able interface, and free support, Filezilla is a dazzling example of an all-around balanced FTP client.
While CyberDuck is a strictly Mac based program, it is still able to compete with multi-platform clients on a functionality basis. CyberDuck offers a clean interface with the ability to bookmark, browse through local and remote connections, and synchronize your Mac with the remote server. CyberDuck is perfect for Mac users, especially if they are using or planning to use on offsite storage solution.
Core is a Windows based FTP client that has all the features necessary for an FTP client and more! With updates that are released frequently and a large population of users, this client is well kept, up to date, and easy to troubleshoot. Core FTP also offers a free version and a paid "Pro" version, which offers more added features. The decrypt and encrypt options built into the client makes the transfers to secure areas safe and easy.
CoffeeCup is a company that was created in a small coffee shop with the dream to create website software that's easy to use and integrate with any control panel. While CoffeeCup can only run on Windows, it is extremely easy to use and mimics the cleanliness of CyberDucks interface. While their free FTP program is only useable on Windows operating systems, they have a huge software selection for OS X systems!
SmartFTP is a popular FTP client that only runs on Windows operating systems (including Windows 8!). This client is highly versatile and well known for its ease of use. With a very thorough tutorial section included right on their website, SmartFTP is great for beginners to expert levels of FTP experience. The knowledge base also gives users a way to troubleshoot their own problems and understand more about FTP programs in general.