Apple iPods and iPhones are frustrating for syncing music. Being loyal to just one system is not good! And SwapTunes allows you to synchronize your iPhone with two PC’s. This is much like the DualDesktop app we use on windows. This app creates two virtual profiles of your iPod and you can switch between these profiles using SwapTunes.
Just take care, don’t sync the profile with the wrong PC…
Installs via Cydia on iPhone v 2.x. Tested on 2.0.2
Cydia is an Installer alternative, that Installs on Jailbroken iPhone 2.x… Info here