You can send e-mail messages and have them show up as a text message on an SMS-enabled phone, if you know the cell phone carrier used by the recipient. Here’s a list that may come in handy, courtesy of a post on the QuarterToThree forums:
T-Mobile
Format: 10-digit cell phone number @ tmomail.net
Example: 3335551111@tmomail.netVerizon Wireless
Format: 10-digit cell phone number @ vtext.com
Example: 3335551111@vtext.comRogers Wireless
Format: 10-digit cell phone number @ pcs.rogers.com
Example: 3335551111@pcs.rogers.comSprint PCS
Format: 10-digit cell phone number @ messaging.sprintpcs.com
Example: 3335551111@messaging.sprintpcs.comCingular Wireless
Format: 1 + 10-digit cell phone number @ cingularme.com
Example: 13335551111@cingularme.comAT&T PCS
Format: 10-digit cell phone number @ txt.att.net
Example: 3335551111@txt.att.netBell Atlantic
Format: 10-digit cell phone number @ message.bam.com
Example: 3335551111@message.bam.comBell Mobility (Canada)
Format: 10-digit cell phone number @ txt.bell.ca
Example: 3335551111@txt.bell.caCellular One
Format: 10-digit cell phone number @ mobile.celloneusa.com
Example: 3335551111@mobile.celloneusa.comComcast
Format: 10-digit cell phone number @ comcastpcs.textmsg.com
Example: 3335551111@comcastpcs.textmsg.comFido
Format: 10-digit cell phone number @ fido.ca
Example: 3335551111@fido.caTelus
Format: 10-digit cell phone number @ msg.telus.com
Example: 3335551111@msg.telus.com
