Choose the menu item iCal > Preferences (or hit Command-Comma within iCal, as that’s the keyboard shortcut for the preferences for most programs). When that window opens, click the General tab, then toggle “Show: [number] hours at a time” to whatever you’d like it to be.
I prefer to change that number to 24; that way, my day view shows me all my events without having to scroll to view earlier and later times. The only downside is that, if you’re anything like me, you’ll continue to attempt to scroll to the bottom of your window even now that there’s nowhere to go. Don’t be like me.
Here’s how the view looks when you’ve told iCal to show 24 hours at a time. A day in the life, indeed.