WinSCP

WinSCP is an open source free FTP & sFTP client for Windows. Beyond file transfer, WinSCP offers file management & file synchronization functionality. One of it's biggest advantages its simple user interface - which mimics Windows Explorer (there is one that mimics Norton Commander as well) in both looks and functionality - making a it extremely user-friendly for an avid Windows users. For me, drag-and-drop feature and the ability to see my folder structure is very handy. Even the tool icons look the same as in Windows Explorer, so you will never get lost, even without a manual or a geeky friend next to you.