The Earth is making its yearly passage through a drifting path of debris left by a comet named Swift-Tuttle. The result? The annual Perseid meteor shower takes place!
You can probably expect to see 30-40 meteors per hour if you're viewing late tonight (Saturday); 45 per hour late Sunday night, and up to 80 per hour in the wee hours of Monday. For comparison, on a normal night any other time of year, the average rate is just 2-3 meteors per hour.
Naturally, the darker the skies, the more meteor streaks you're going to be able to see.
Why is this shower called "the Perseid shower", you might wonder? The meteors are entering the Earth's atmosphere in a small area in the direction of the constellation Perseus. This means is that if you trace the direction of the meteor streaks backwards, you will observe that they are "emanating" from Perseus. But you don't need to focus your gaze on any particular place in the sky to see them--just lie down and look around. (Reclining lawn chairs are a meteor-watcher's best friend.)
However, it may be the case that the higher in the sky Perseus is, the more meteors you are going to be likely to see. In other words: the later you view, the better. For locations in central and eastern North America, Perseus will be an "acceptable" altitude of 20 degrees above the northern horizon by 9pm to 10pm (an hour to two hours later if you're further west). If you're familiar with the W-shaped constellation of Cassiopeia, Perseus is just "below" that. The Stellarium screenshot below shows Perseus (far right) in relation to Cassiopeia, the Big Dipper (at far left), and the northern horizon. Click on this image to see a much enlarged version open in a new window:
In my experience,the Perseids are the best meteor shower of the year. Not only are they more numerous than most of the other annual meteor showers, but they occur in summer, a reasonably pleasant time to be outside at night. (Just don't be deceived: take a jacket!). It's especially nice that this year they've conveniently decided to occur on a weekend and a New Moon. : )
So, don't miss it!
(For more information: this article at Sky & Telescope has much of the same information as above, but contains a few additional interesting details.)