SyncJe from NextHaus is another option for syncing calendar info to SyncML, although I think the price is way too high right now. I'd suggest waiting a week or two for the iPhone 2.0 software update. There might be some kind of built in syncing (although it may require subscription for .Mac/MobileMe) or at least you could install an application like SyncJe (if they release it in the App Store, the price will be much cheaper).
Thanks for the suggestions. I have a friend who has a Nokia with built-in SyncML and I'm so envious at how easy he can sync his calendar and contacts over the air. Hopefully the 3G iPhone has this functionality. And let's hope .Me or MobileMe or whatever they call it has a reasonable subscription rate... not like the ridiculous $99/year for .Mac. Is it me or does everything these days require a subscription? It's driving me crazy!