There are multiple ways to use email to send text messages to someone's cell phone.  
 
   If you have something quick, try using the web page: http://www.onlinetextmessage.com/

   To create email address book entries:
   Insert the destination phone number using the recipient's carrier address as per below:
 

Verizon: phonenumber@vtext.com
AT&T: phonenumber@txt.att.net
T-Mobile:  phonenumber@tmomail.net
Virgin Mobile:  phonenumber@vmobl.com
Sprint: phonenumber@messaging.sprintpcs.com
Cingular: phonenumber@cingularme.com
Nextel:  phonenumber@messaging.nextel.com
Alltel phonenumber@message.alltel.com
Boost Mobile phonenumber@myboostmobile.com
Rogers Canada phonenumber@pcs.rogers.com
Teleflip phonenumber@teleflip.com