Updated 06/15 to include the latest version of Android OS on the phones and added MyTouch Slide.

Less than two years after Google introduced the first Android phone, the free, open source operating system has turned into a juggernaut. There are 17 Android phones available today, and three new devices will hit retail stores in the next few weeks.

The latest Android phone is the HTC Aria. AT&T revealed the Aria on Monday as a mid-range phone that will run Android 2.1, have a 5-megapixel camera, a 3.2-inch display and a slower processor than the Nexus One or HTC Evo 4G (the Aria's CPU clocks 600 MHz, compared to 1 GHz on the latter).

Aria is not the last Android phone from AT&T this year. The company has said it will have five Android devices in 2010 and is likely to announce yet another Android phone soon.

Google debuted the Android operating system in 2008, and the first handset to use it was T-Mobile's HTC G1. Since then, the four major U.S. wireless service providers – Verizon, AT&T, T-Mobile and Sprint – have embraced the OS. AT&T's Android portfolio, though, is the weakest, which shouldn't be a surprise considering its exclusive deal with Apple: Thanks to the success of the iPhone, AT&T has less reason to explore Android alternatives.

From the $50 LG Ally on Verizon to the most advanced handset available today – the HTC Evo 4G on Sprint – there's an Android phone for almost every price range and level of use.

So if you are looking to switch to Android or upgrade your existing device, check out our list of all the Android phones available by wireless carrier. Prices mentioned below are those listed on the website of the carrier, with a two-year contract, except as noted.

For more details on each of these phones, click through to the carrier sites: AT&T, Sprint, T-Mobile and Verizon.

Photo: Android mascot (Esti/Flickr)