The countdown (or up) has begun on Apple's one billionth app downloaded. Apple has posted a web page with a ticker actively displaying the number of downloaded apps (paid and free), which is now closing in to the one billion milestone. In celebration of this accomplishment, the company is giving away a $10,000 iTunes Gift Card, an iPod touch, a Time Capsule and a MacBook Pro.

How do you get in on the action, you ask? Simply head over to App Store and download an app to be automatically enrolled. Alternatively, to enter the contest without downloading anything, enroll via the form here. Regardless of the method, according to the contest rules you're allowed to enter up to 25 times per day.

As an interesting addition to the ticker page, Apple has provided a list of the "all-time top 20 apps". A few of the top paid apps include Crash Bandicoot Nitro Kart 3D, Koi Pond, Enigmo, Bejeweled 2 and iBeer. Some free apps to make the list are Facebook, Google Earth, Pandora Radio, Tap Tap Revenge and Shazam.