Upload only changed files to your site, even monitor folders for changes, with WinSCP
WinSCP is a free FTP and SFTP client for Windows. Legacy SCP protocol is also supported. Its main function is safe copying of files between a local and a remote computer. WinSCP is one of the finest FTP clients you will find.
Features: Translated into several languages; Integration with Windows (drag&drop, URL, shortcut icons); U3 support; Batch file scripting and command-line interface; Directory synchronization in several semi or fully automatic ways; Integrated text editor; Support for SSH password, keyboard-interactive, public key and Kerberos (GSS) authentication; Explorer and Commander interfaces; Optionally stores session information; Optionally supports portable operation using a configuration file in place of registry entries, and more.
With WinSCP you can synchronize directories by uploading and downloading the changed files. For this you may find useful features like Synchronize Browsing and Compare Directories or transfer option Newer and updated file(s) only. You can use function Synchronize to let WinSCP do the synchronization for you.
If you make your changes locally and immediately upload the changed files to remote directory, you can make this much easier by letting WinSCP watch for changes you make and automatically reflect them on the remote directory using the function Keep Remote Directory Up To Date. If you happen to have the same files locally and remotely with different timestamps, you can update them without transferring the files again. Use function Synchronize in Synchronize timestamps mode.