You can send email to cell phones. Here are the addresses for the top six US carriers. Substitute an actual phone number, send the e-mail and it will arrive as a text message.

T-Mobile             phonenumber@tmomail.net

Virgin Mobile       phonenumber@vmobl.com

Cingular               phonenumber@cingularme.com

Sprint                  phonenumber@messaging.sprintpcs.com

Verizon               phonenumber@vtext.com  

Nextel                 phonenumber@messaging.nextel.com

Or you don't know the cellular service company, go through a third-party service, rather than direct e-mail, consider using http://www.teleflip.com. Teleflip automatically sends e-mail to the proper service provider when you enter the 10-digit phone number.