The trick involves a couple of Terminal commands. To enter debug mode, use the following:
defaults write com.apple.iCal IncludeDebugMenu 1
And, if you want to remove it, use the following command:
defaults write com.apple.iCal IncludeDebugMenu 0
Once you've got the debug menu activated, restart iCal. Here's what you'll see.
There's quite a few tricks here, including the ability to have to multiple iCal windows open at the same time. You also can expand the week view to glimpse up to 28 days at once, which is a little too much. But like ZDNet says, being able to see two weeks at a time in week view is pretty handy.
To switch the views, select the desired time from the "top sekret" menu and toggle between week and another calendar option. The new mode is enabled once you return to the week view.