I've been toying with Microsoft Live Mesh... and I'm very surprised that it has so much functionality and so far works VERY well.
I hardly have to think when selecting folders to synchronize. Best of all, Live Mesh syncs between Mac and PC! That's right! I'm able to synchronize my pictures, music, and documents between computer systems OVER THE WEB! This synchronization happens in real time and regardless of location. If I'm at home, or work, or abroad, my photos are kept synchronized between my MacBook Pro and my home desktop... now THAT is impressive!
If you have the need to synchronize documents, pictures, and music between two computers Microsoft Live Mesh may be right for you! I understand it also works with some mobile devices, but I didn't see an Android application on the Market when I did a quick search, so I've not tested that.
I'm not getting paid by Microsoft... I just like to share with my friends and family when I find a good solid product (especially a great FREE service). I'll be testing it out for a few weeks and I'll give you an update when I learn more.