Freeware if you can deal with occassional nag-screen.

Now supports FTP and Powerbuilder and SourceForce code versioning.
* Synchronize files between PCs, hard drives, client/server networks, and laptops.
* File SyncForce now supports file storing – versioning via SourceForce (online video explains use), a simple yet powerful file-based source control versioning system – a differencing system which saves only the differences between file versions, saving lots of disk space. Also, you can zip up the these difference files, to lower the number of files on your system, keeping your directory organized, while yet saving more disk space via differencing and zip compression – very powerful for any c,pascal,java,delphi,VB,C#,C , programmer backing up code.
* Restore file/files from 2 years ago with SourceForce version control.
* Automatic scheduled syncs and backup operations.
* FindFiles utility included with powerful file/ftp/powerbuilder search client.
* Options...
-Single destination folder;
-Include emtpy subfolders;
-Compare using file size;
-Compare using file contents;
-Move File;
-Sync Deleted files;
-Overwrite is destination is newer;
-Move/Rename Dest on change;
-Search by filename;
-Search by file content;
-ASyncronous detect (immediate backup);
-AutoDetect via exact time or time interval;
* Network traffic is minimized – Copy files from network to your local machine – work locally.
* Prevents data loss from update conflicts – will make a backup if both source/destination files have changed.
* Backup of files on change option for version control.
* Difference backups option for version control.
* Zip backups for clean version control.