Here is an iSync plugin I have written for the Nokia 6600 Slide phone. (download)
To install:
Unzip to your desktop
Open up finder and go to your Home Folder -> Library
If the folder PhonePlugins (no space) doesn’t exist, create it
Copy Nokia-6600-Slide.phoneplugin to the PhonePlugins folder
Restart iSync then add a device
Please note that this works for my purposes, [...]