If you have large music library in your iTunes then syncing with iPhone or iPod touch could be very slow to speed up iPhone & iTunes sync here is excellent freeware utility BackOff.
BackOff is a PC and Mac utility enabling you to Speed Up the Sync of your iPhone or iPod Touch by turning off the automatic backup in iTunes. Storage of large amounts of data can seriously lengthen iTunes sync. Disable iTunes Auto-Backup feature with BackOff and speed up your sync !
Features of BackOff
1. BackOff is free
2. One Click to Turn Off / On
3. PC Windows (XP, Vista, 7) & Mac OSX (Tiger, Leopard, Snow Leopard) compatibility
4. Supports iPhone V1, 3G, 3G S & iPod Touch V1, V2 and V3
5. Supports iTunes 9.0.2 (iTunes 9.0.3 is available for download)
Download BackOff to Speed up iTunes and iPhone Syncing.
Please Note: Turning OFF automatic backup of your iPhone or iPod Touch in iTunes speeds up syncing, while important data is not backed up. Use with Care!