Backstory - I've had a work phone for years now, to the point where I don't have a personal cell. The company has an unlimited voice and data plan, but (smartly) no sms messaging. This comes at great frustration to my friends in that they wonder why I'm never privy to the plans they've already made. To which my response is constantly "I can't get texts!".
So then Google Voice goes public, and now all is right with the world.
What you need
-A cellphone with email capabilities (IMAP or POP3)
-A Google Voice account (and gmail address)
What you do
-Sign up for a Google Voice account and get your new phone number
-Enter your contacts' phone numbers in Google Voice
-Goto Google Voice Settings -> Voice Settings -> Voicemail & Texts
- Check Text Forwarding
-Setup your gmail account on your mobile phone (IMAP works best because it's instant delivery)
-Send a text to all of your friends from the Google Voice account saying something like "It's me, save this number in your phone as [Name]Text."
-When they respond it will forward to your gmail account
Now you have a phone number dedicated to just text messaging which will instantly forward to your gmail account and thus, to your phone. When you receive the text you can just reply to the email and it will automatically forward to their phone as SMS.