One of the text message utilities I have been using for years is Teleflip.  Rather than waste my money on text messaging friends and colleagues from my cell phone.  I use this service.  I find it much faster to type out a quick email to them than screwing around with the keys on my phone.  Just click on the image below to try out Teleflip.

Another cool thing you can do with Teleflip is enter in the cell number you want to contact into your email.  I find this a lot more beneficial than going to their website every time.  You just need to type in 1(555)-555-1234@telefip.com and send the text message on its way.  Then you can save that contact to easily text message your contacts from email.  *Note I have only tried this with my Yahoo Email account and it works, so I cannot speak for any other services.  If you have information on other services definitely share them with us!