Folder Synchronization recommends the following folder synchronization programs:

Three-way file/folder comparison:

Araxis Merge 
Guiffy 8.0 
ECMerge Pro 2.0

Two-way file/folder comparison:

Beyond Compare 2 
ExamDiff Pro 

Folder synchronization (no file comparison functionality):

Heatsoft ADCS 1.20 
ViceVersa Plus 

The BEST folder synchronization tools include the following advanced functionality:

- user friendly interface
- comparison by name, by date/time, by size and by file content
- folder tree synchronization
- byte-by-byte comparison
- creating folder snapshot
- powerful file filters
- file management capabilities (change attributes, open in third-party application, rename or delete)
- “Undo” option (all automatic/manual changes in the compared folders are not immediately applied on the hard drive)
- Version Control integration

We could also mention the following useful functionality available in some synchronization tools:

Comparing numeric versions of files (CRC):

Beyond Compare 2
ExamDiff Pro
ViceVersa Plus
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Immediate notification on changes in the compared folders:

ExamDiff Pro