Can you sync now contacts with an iphone?

You cannot "sync" contacts from Now Contact to the iPhone, but there are several possible solutions depending on what you want to do.

Now X, which is currently in Public Beta, syncs with the iPhone through Sync Services on the Mac and can import your Now Contact data directly.

You can also move contacts from Now Contact to AddressBook pretty effortlessly and sync AddressBook to the iPhone. If you are using Mac OS 10.4 or earlier with Now Contact, you can use the "File -> Synchronize -> With AddressBook..." option. If you are using 10.5, you can drag all your contacts out to the desktop and drag them into AddressBook (this isn't a sync, it's an export import).