My first pass at Outlook/Palm to iCal/iPhone calendar migration was to stop using the old calendar, and start a new one.
Then I realized how long it would take to tediously enter birthdays and the like, so I decided to migrate calendars from my Palm using Missing Sync for Palm.
(Warning: if you do this, I suggest renaming your iCal calendar so it can't possibly clash with any Palm category you might have.)
(Note: I'm still on 10.4, though now I'm scheduling the 10.5 migration. So 10.5 behavior may vary.)
It worked, but when I was done all the Categories in the Palm had become calendars in iCal.
This is why synchronization is so horribly hard. Application models vary. The Palm allowed for one calendar, but each appointment could belong to a single one of about 9 categories. Google has an unlimited number of Calendars, but no categories. Outlook 2003 has one real calendar, but each appointment can be associated with an unlimited number of categories. Outlook 2007 is similar, but it supports calendar overlays. Google is like iCal, but appointments can have locations. Alerting models all vary.
I won't even mention how astoundingly limited iCal is compared to even Outlook 2003 -- with one huge exception. iCal can subscribe to calendar feeds. Still the absence of a list view in 10.4 is surprising -- even the iPhone calendar has a list view.
Anyway, since I sync a single iCal calendar with a single Google Calendar, I wanted to merge some of my iCal Calendars. Turns out the way to do this is to export the calendar you want to eliminate, then import it back into the target Calendar.
The good news is that somehow I've gotten closer to Calendar Nerdvana than I'd expected. Between synching iCal to gCal with Missing Sync, my wife's Blackberry synching to gCal with a built-in app, and my subscribing in iCal to my wife's Google Apps family calendar, I'm starting to be able to get useful calendar overlays. Now if I figure out a work calendar solution ...