Snow Leopard makes looking at event details in iCal easier. In the Leopard version of iCal, you had to double-click an event to reveal only some information in a pop-up box; you then needed to click the Edit button (or press Command-E) to edit an item's information. In Snow Leopard, choose Edit > Show Inspector (or press Command-Option-I) to bring up a floating inspector that provides an editable view of any items selected in your calendar.

From Doug McLean