Out the box it is not possible, though there are some third party options that make this possible (in part anyway). I am currently synching my Lotus Notes contacts and calendar with my Iphone, using a third party solution from Companionlink to facilitate transfer of info between my Iphone and Lotus Notes. I was only required to also have Outlook and Itunes on my machine to make this possible. This doesn't sync e-mail though. Microsoft has an outlook add-in, which apparently will give you the same functionality, when used with Itunes, though I haven't tried this.
The other solution which is useful to get the data to iCal is to synch with google calendar with companion link and then use Spanning Sync to get the google to your mac's ical. I read a rumor that mNotes is going to likely support iphone for wireless data push like the blackberry but I cant confirm it.
For email, I've started using VistoMobile. This will sync your lotus notes inbox with your iphone using an IMAP configuration. It requires a desktop client and only available on windows.
VistoMobile provides a web lookup to the corporate directory. This is limited to email, at this point, and only allows an email to be created with a single address.
For Calendar entries, I setup a forwarding rule in Notes to forward meeting requests, updates, etc. to a Live Mail account. Using the httpmail plug-in for Leopard, I can access these on the MAC to update ical, even from behind the corporate firewall.
Entries that I add on the iPhone, I forward to the corporate account once they are sync'd with iCal. Not ideal, but it works ok for me while I wait for a single complete solution.
When creating a meeting / appointment in lotus notes I include my Live Mail address as an attendee. This facilitates getting the meeting scheduled in iCal. Most of the time, these are accepted without any intervention once the email is downloaded.
