IDrive Lite is a neat free application that allows you to backup, share and restore your iPhone contacts completely free of charge if you’ve updated your iPhone software to 2.0. You just need to install the Open IDrive Lite app on your iPhone. Tap the 'Backup' button to backup all your contact information, including names and numbers. And just click the 'Restore' button to get back all the contact information on your iPhone. The Restore process is smart enough to leave new contacts untouched and only restore contacts that are missing.
More info: IDrive Lite