http://discussions.apple.com/thread/2759427?answerId=13110776022#13110776022
- "To prevent a sync when plugging in the iPod/iPhone - hold down the 'option' and the 'command' keys when plugging in the iPod/iPhone - key the keys down until the iPod/iPhone is listed under the Devices list in iTunes - this will prevent a sync from taking place and you will be able to change your settings." - overrides Mac preference setting to automatically sync.
http://www.technipages.com/iphone-ipod-touch-ipad-prevent-automatic-sync.html - Mac and Windows, disable all automatic syncing or manually override automatic syncing on specific occasions.
iTunes Store: Transferring purchases from your iOS device or iPod to a computer - http://support.apple.com/kb/HT1848
Commercial software utility for transferring songs from i-device to Mac - http://www.fadingred.com/senuti/