Lorenzo Puleo has released a new beta version of the file sync/back up tool, FolderSynchronizer. Version 1.6b adds stability and performance enhancements. According to Mr. Puleo:
The best way to synchronize or backup on Macintosh. Choose two folders and then they will be synchronized exactly. FS can filter the documents to copy, by Type, Creator and Modification Date. FS can do multiple Synchronizations or BackUps from your custom lists. Scriptable by AppleScript.
FolderSynchronizer is available as shareware for US$20. You can find more information at Lorenzo Puleo's web site.