Today is a big day for Android on the AT&T network. In addition to the Bravo and Flipout, AT&T is brining the Motorola Flipside to market.

The Motorola Flipside will be available for $99.99 with a two service agreement and 2 year smartphone data plan in AT&T stores, online, and in business channels by this holiday season — no mail-in or “instant” rebate required.

Running Android 2.1, the latest version of Motorola’s MotoBlur UI, and a relatively large QWERTY keyboard, the Flipside is AT&T’s answer to T-Mobile’s G2. It sports a 3.1-inch multi-touch HVGA display, and most notably a huge trackpad. AT&T is selling this as an “alternative way to navigate” and providing a better one-handed experience with the device than other Android devices.

Like the Flipout, the Flipside sports a 720MHz processor, 512MB of both RAM and ROM, Bluetooth, and 802.11 b/g, but ups the battery to 1540mAh (probably to power the higher resolution, 320 x 480 screen). Also on board are the same three-megapixel shooter we’ve been seeing all day, presumably lacking a flash as well.

Update: Article updated with new spec information.