You may know that you can double-click on a Mail message (or hit Command-O) to bring it up in its own window. Continue doing this with as many you want, and Mail will obediently open a window for each message. But it’s less well known that you can do a similar thing in Address Book and iCal, which is pretty darned useful for comparing data. In Address Book, for example, double-click on each contact you want to open.
As you can see, each contact card will open in its own window, allowing you to compare or edit the information within them. I find this especially useful when I’m trying to weed out duplicated data.
Similarly, double-click on events in iCal to pull them open one at a time.
Note, though, that you have to have the preference Open events in separate windows turned on in iCal for this to work. That checkbox is within the menu item iCal > Preferences, under the Advanced tab. If you don’t have that on, double-clicking an event will only open the little pop-up beside it, and you won’t be able to open any others at the same time.
If you want, you can pick up, drag, and drop that pop-up to force it to become its own window instead of it being attached to its event, but that’s adding an extra step to the process.
Drag an event’s pop-up to pull it out into its own window.
I’m not fond of extra steps. (But I am awfully fond of the Open events in separate windows preference, anyway.)
Finally, in both Address Book and iCal, the keyboard shortcut for “open the things I have selected in their own windows” is Command-I. In iCal, that’s invoking Edit > Get Info; for Address Book, that’s Card > Open in Separate Window. So you can hold down Command and select as many cards or events as you like, hit that keyboard shortcut, and zowie! They all open up without you having to double-click each one. Why, you could have a screen full of contact cards if you wanted. I don’t know why you would, but you could.