And got a bit of push, too (without paying a dime).
Instead of uselessly duplicate your information over the net (or paying Apple for its expensive Mobile Me service), you can just use Google and synchronize the information you need on your iPhone. The instructions are very easy and can be found on Google Sync home page. Basically the service uses aMicrosft Exchange account to set up synchronization for contacts, calendars and, who knows, possibly mail in the future.
I'm very happy with the service. That's the best approximation to push I've reached so far with my iPhone.
Just one warning for non-English users: when I did set up my iPhone, I went to the Sync home page with the iPhone integrated web browser just to discover that the service is not yet available for my phone model. That message was shown in Spanish language. Switching Google's language to English let me access the Sync service options instead.