Good back-up / sync tool

What is a good tool to have scheduled synchronisation between folders?
The idea is to have a back-up of certain folders on an external device and let the tool monitor changes and execute them on the backed up folders at predefined intervals. This so I don't have to run a daily +20GB backup.

On my windows machine I used Syncback, which monitors the folders you want and synchronizes the changes to an external USB device.

SuperDuper! is great, as it will create a fully bootable backup should you need it and can backup to network devices as well. It allows you to simply update your previous backup, and if you buy the full version you can schedule it to run in the background.

On the other hand, you have Time Machine that is built into Leopard which is also capable of syncing backup and original.

Does anyone have any idea when Carbonite.com is going to be released for the Mac?? I have emailed them twice and received no response. I use it on the PC and really like it!!!

I use ChronoSync daily and it works great!