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You have many choices when it comes to smart phones. If you want a touch-screen smart phone, though, you start limiting your options. Here, the Apple's iPhone and phones running Google's Android operating system dominate the touch-screen smart phone market. They're your best bet.

Palm and BlackBerry-maker RIM haven't released new models in months. Microsoft is preparing to release Windows Phone 7 by year's end. It should offer big improvements over Microsoft's current phone software, like multitouch.

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Let's look at the hottest new touch-screen smart phones.

iPhone 4

The iPhone 4, available in black or white, comes with either 16 gigabytes of memory for $199 or 32GB for $299. Apple will continue to sell the 8GB version of the iPhone 3GS for $99.

The most striking feature of the iPhone 4 is its design. The front and back panels are made of aluminosilicate glass. This is used in windshields of high-speed trains and helicopters. They're joined by strips of stainless steel, which function as the antenna. At roughly one-third of an inch thick, it is the thinnest smart phone available.

The camera features a 5-megapixel back-illuminated sensor. You'll take better photos in low light. And the LED flash works with both photos and videos. A second, front-facing camera allows video chats with other iPhone 4 owners over Wi-Fi.

The iPhone features 720p high-definition recording at 30 frames per second. This should provide smooth, high-quality video. Videos can be edited directly on the phone. The 3.5-inch retina display offers an astounding 960-by-640-pixel resolution.

Battery life is also improved. Talk time is seven hours and standby time is 300 hours. On the downside, the iPhone doesn't support Adobe's Flash. This means not all Web pages will display properly; you won't see as many online videos.

To check your upgrade eligibility, dial *639# from your current iPhone. AT&T will text your upgrade eligibility.

HTC Evo 4G

HTC's Evo 4G ($200) is flying off shelves. This Android phone is the first phone to use 4G. This technology promises faster data speeds, but Sprint's 4G service is only available in a handful of cities. The Evo supports up to 32GB of storage via a microSD slot; an 8GB card is included.

The Evo offers a 4.3-inch display with 800x480 resolution. There's an 8-megapixel camera on the rear with dual LED flashes. A front-facing camera can be used for video calls. The rear camera records 720p video at 25 frames per second. You may notice some choppiness in your videos. A micro HDMI port connects the Evo to your television.

One of the Evo's cooler tricks is its hot spot feature. Sprint says up to eight gadgets can connect via Wi-Fi. The phone also supports Sprint TV. You can watch live broadcasts and other programming from a variety of channels. For example, NBC, ABC, ESPN and Disney provide programming.