Phones that let you send text messages have been around for quite some time, such as the Motorola RAZR (or really any phone that has a text messaging plan). That's because each phone number represents a series of letters, and when you're in text mode you can press each number multiple times to cycle through the letters associated with that number.
But that's the hard way to text, or at least a very SLOW way to text.
Enter the Querty keyboard that you find on iPhones and Blackberries. These keyboards give you the full alphabet along with other characters like commas, exclamation points, and quotes. They also let you use both of your thumbs to bang out a text message in a few quick seconds.
The drawback with iPhones, Blackberries, and most other Qwerty devices is that you usually are required (at least if you're using AT&T) to purchase a data plan that includes web browsing and email.
These data plans cost about $30 extra a month, in addition to text messaging support that can range from $5 a month to $20 a month depending on your phone carrier and whether you have unlimited texting or just a couple hundred texts a month (which is very easy to burn through in just a few days).
If all you want from your phone is text messaging, but want to be able to text quickly and easily using a full Qwerty keyboard, then take a look at the LG Xenon from AT&T.
The Xenon comes with a full slide-out Qwert keyboard for fast texting, and also gives you a 2.0 megapixel camera with flash and video recording capabilities, GPS navigation, calendar, contacts, games... essentially a full blown Smart Phone.