It doe not support Lotus Notes, however there are ways to sync the data from Lotus Notes Calendar and Contacts into outlook using a product from a company named CompannionLink and then you sync your iphone from there.
Also if you are interested in syncing your mail with Lotus Notes a company called Martin Scott has a product called WirelessMail for Domino which will install a Lotus application on your Notes Desktop, which will copy all your e-mail into a gmail or yahoo account and once ther you can just add the e-mail accout to your iPhone and magic...e-mail from Notes.
The only problem is the cost for Calendar and Contact Sync you have to buy Outlook and then CompanionLink which will run about $180 or so for both