If you’ve got a smart phone it doesn’t make much sense to pay $5, $10 or more a month for text messaging plans once you realize you can send free messages to friends’ phones via email. All you need to pull off the trick is your text-ees’ phone numbers and service providers.
A Popular Mechanics post from last year rounds up the formulas:
Once you add your friends’ cell emails to your contacts, it’s just a matter of firing off a mass email telling them to text you at your email address from now on.
How to Email Text Messages to Any Phone [Popular Mechanics]