While the iPhone and its more than 300,000 applications are forever changing how we interact with handheld devices, Apple’s (AAPL) iconic smartphone is no longer the only game in town.

Google’s (GOOG) Android mobile platform now powers many different phone models that combined – according to Nielsen – outsold the iPhone nationwide in the first half of 2010. This lead figures to increase if rumors that Sony will soon unveil an Android-powered PlayStation Phone are true. Even more telling, the Android Market – Google’s version of the iTunes App Store – now has more than 100,000 Android apps available to download.

So while Apple remains the clear leader in mobile applications and continues to push the envelope in terms of what is possible on smartphones and tablet devices, there are many cool Android games, web browsers and apps for all walks of life that currently can’t be tapped into on the iPhone. So which ones are worth downloading?

Great games exclusive to Android

Robo Defense ($2.99)

It’s jolly old England and enemy knights want to invade your castle. You need to strategically erect towers as your last line of defense. As the enemy waves keep coming, you must upgrade your weapons and buy more towers to protect the territory. Fun graphics and challenging scenarios will keep you battling. If you succeed, you’ll earn a seat at the Round Table. Sure, there are several tower defense games for the iPhone, but this title stands on its own.

Gem Miner: Dig Deeper ($1.99)

Ripped from the headlines, Gem Miner features a courageous miner willing to dig for coal and precious gems in an unstable mine. You decide whether to keep digging, prop up more support beams, or skeedaddle to surface before the shaft caves in. Pace yourself, because mining is hard work, and if the Stamina gauge drops to zero, the miner falls over dead.

Gamers with Android phones can also download Adobe’s Flash Player to access hundreds of thousands of web-based games and videos. Steve Jobs hates the popular Flash interactive animation and video format, so don’t expect it to run freely on the iPhone anytime soon. The Flash Player can vary between devices and versions of Android’s operating software.

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Browsing more freely on Android

SkyFire Browser (Free)

Don’t like your phone’s web browser? On Android, you can download a new one! Skyfire delivers fast web page loading and cool features like tabs and a toggle to jump between mobile and desktop views of a web page. Mobile video, including the iPhone-banned Flash video format, plays smoothly. Let SkyFire scan the pages you view and find related web pages and Twitter feeds.

Dolphin Browser HD (Free)

Customization is king in this mobile browser. You control it by using finger gestures like drawing an up arrow to scroll to the top of a page or a down arrow to go to the bottom. Not enough? Dolphin HD lets you create your own gestures. Download add-ins to manage bookmarks, tabs, themes, RSS feeds, and more. New add-in choices appear regularly.

Google apps made only for Android phones

Google Sky Map (Free)

Be the hero around a campfire! Point your Android phone at the night sky and – using GPS technology as well as a compass, date and time – Sky Map will show you exactly which stars you see and the constellations they comprise. Move your phone to view other stars and planets or switch to manual mode where you drag the sky around on your phone’s screen with your finger. What’s most amazing is that if you search on any sky object, Sky Map will guide your hand with on-screen arrows to find it overhead.

Google Voice (Free)

Google Voice redefines mobile communication and it is integrated into Android phones. When you receive a voicemail message, it is automatically transcribed and sent to your voicemail box. You can then read or listen while the spoken words appear highlighted as the message plays back. Text messages cost nothing when sent through Google Voice. You can get cheap international calling rates, one number to ring all your phones, custom greetings for different callers, and much more.

Fans of Google-developed applications should also check out Google Maps, which lets you speak your destination out loud and offers turn-by-turn navigation for free on Android devices only, as well as augmented reality-based search engine Google Goggles. Both of these apps are free.

Phone customization is much easier on Androids

Tasker ($6.30)

This app lets you program your Android like a robot. Ask Tasker to launch your Pandora Radio app whenever you plug in your headphones. Or, have your phone send a text message home telling your family you’re almost there, whenever you reach your highway exit. Tasker automates actions based on date, time, location, events, and more. The setup is easy and very flexible.

LauncherPRO (Free)

Don’t bother trying to customize the iPhone’s home screen. Beyond moving icons around or updating the wallpaper, it’s locked. Not so on Android. Personalize your home screen in seconds with new menus showing things like battery life, calendars and chat all in dynamic widgets. Bored? Simply change the menus again.

Worthy apps on other platforms

All in all, the Android Market delivers plenty of choices. But, feel free to keep shopping. Microsoft (MSFT) just released its Windows Phone 7 operating software, which already has more than 1,000 apps. Exclusive offerings on that platform include the science fiction role-playing game The Harvest, as well as tight integration with Microsoft’s Xbox LIVE gaming platform.

Not to be left behind, RIM (RIMM) recently rolled out the 2.0 version of Blackberry App World, with easier access to thousands of apps. While neither Microsoft nor RIM apps are in the same league as Android, Google has already shown that lots of progress can be made in the app space in a very short period of time.

 

Editor's note: We removed an app listed in an earlier version of this story after further investigation.