The calendar you're currently viewing (or all calendars if you're viewing all) on your iPhone can be searched easily.
1. Run the Calendar app
2. Select List from the bottom menu
3. Enter the search term in the search field at the top of the screen
Invitees, Locations and Titles of your events will be searched as you type. For additional results touch the Search button.
Yes, the iPhone supports subscriptions to both calendar formats. Several calendar-based services, such as Google, the Mac OS X iCal application, and Yahoo! support both formats. To subscribe to a calendar on the iPhone:
1. Navigate to Settings -> Mail, Contacts, Calendars -> Add Account
2. Select Other -> Add CalDAV Account or Add Subscribed Calendar
3. Enter your account information and touch Next
4. Touch Save
UPDATE: Apple will include .ics support in iOS 4.2. Release date is November 2010.
We get a lot of emails asking something along the lines of "why does my iPhone not read/recognize .ics files?" The question itself is the answer.
Despite the fact that the OS X Mail App handles ics files just fine (displaying the event/meeting details within the email window, and entering the meeting info into iCal when the attachment is clicked), the iPhone completely lacks this support.
