I haven't tried his any other apps yet, but when I was in the info window in iCal, I noticed that when I tabbed out of the last of the date fields, the highlight kept going into the pop-up menus below. After some experimenting, I discovered you could open the pop-up menu by pressing space bar. From there, arrow keys and Return finish the job. So you can work through all the options without having reach for the mouse, if you are so inclined.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20031029140216659