Why does it take so long to sync photos for my iPod touch  in iTunes?
Find the "iPod Photo Cache" (for iPhoto, it should be listed in iPhoto Library, just right click and select the "Show package contents") and delete it (don't worry, the contents will be recreated the next time you sync). 

Sometimes the data in that directory can get corrupted, causing undesirable effects to happen. Hopefully this will help alleviate your problems.

The directory stores every picture that has been synced with your devices. You can read more about the directory here and ways of deleting it: http://support.apple.com/kb/ts1314