Here are some of the Synchronization tools that I find extremely useful:
Google Browser Sync: If you use Firefox like me, I am sure you would just love this extension. This synchronizes all the Firefox information (Bookmarks, Settings, Cookies and even open tabs) across multiple computers. I use it to sync my home and work computer.
Microsoft SyncToy: If you want to backup your data or keep data across multiple computers synchronized, this is a nifty little tool. It's very lightweight and very intuitively designed. It synchronizes automatically when you change a file from the source to the destination. I use it to keep my data backed up in an external hard drive. Works with Windows XP SP2 only.
Float's Mobile Agent: If you have a Sony Ericsson phone, this is a must have software. It's an open source Sync Software for your Sony Ericsson phone (other phones are being added) using which you can see all kind of information about your SE. You can even answer calls from your PC using this software. But I must warn you that the software is pretty unstable atleast with my SE W810i.