Googles mobile operating system has become the most popular in the United States, and that can only bode well for Motorola, which just unveiled several new Android-based smartphones.

Androids growth also looks good for AT&T. Sure, the carrier owns the Apple iPhone market in the United States but that doesnt mean it doesnt want to capitalize on Androids popularity, too. So Motorola designed three of its new devices for the AT&T network. The Bravo, Flipout and Flipside could be considered the smartphone for budget-conscious customers. They range in price from $80 to $130, and feature Android version 2.1 in other words, not the latest software. Still, all three phones support Wi-Fi and 3G, and come with a 3-megapixel camera.

Motorola also included its Motoblur interface, which syncs information from sources including user contacts, e-mail account and social networks.

Meantime, Motorola is getting into the enterprise-user market, hoping to push BlackBerry maker Research In Motion to the brink. At the CTIA show this week, Motorola took the covers off the DROID PRO, which the company bills as the first Android-based smartphone optimized for business use.” The handset features corporate-level security, a unified calendar, Quickoffice Mobile Suite, a 1GHz processor, 4GB of memory and a QWERTY keyboard.

The DROID PRO will be available on the Verizon Wireless network, which was the first to offer Android-based devices; pricing has yet to be announced but already, the DROID PRO is being called heaven” for BlackBerry fans who want to switch to Android.

And finally, Motorola released yet another device for Verizon this week, the CITRUS handset intended as an affordable, entry-level, customizable smartphone experience in a compact design that is easy on both the eyes and the earth.” Thats because the CITRUS housing is made from 25 percent post-consumer recycled plastic, is certified as carbon-free through an alliance with Carbonfund.org, and is free of PVC and BFR.

The CITRUS has a QWERTY keyboard, a Web browser pre-loaded with Microsoft Bing and Google applications and a touch screen. But, like the three phones headed for AT&T, the CITRUS runs on an outdated version of Android probably because the devices dont have the processing chops to accommodate the latest and greatest edition of Android.

The Android-based phones should serve as a boon to Motorolas struggling handset business. The manufacturer desperately wants to regain its status as a mobile-device innovator, and Androids cachet is sure to help that happen. Thats especially true if the DROID PRO is as awesome as it appears to be. Seriously, RIM, watch out.