If you are sick of those tiny cell phone keyboards and you want an easy way to text without cramping your hands, Tree SMS brings texting to your keyboard with its address book plugin for Mac.  

The text messages can be bought in blocks of 100 and cost around 15 cents per message.  The cost is a bit pricey but the convenience may sway you to using the service.  The application also allows for texting from an iPod touch thru its safari browser.  The concept is a good one but if the texting was 5 cents, this app could be a nice addition for everyday use.  You do avoid roaming costs though which could be significantly more.