Here is something I use quite often, texting from your computer. the only thing you have to know is who their mobile carrier is. once you know that you simply send them a email from your computer and they get it as a text. if they reply it goes back to your email address that you first sent it to.
find their carrier below and simply add thier phone number to the email address:
Alltel
[10-digit phone number]@message.alltel.com
Example: 1234567890@message.alltel.co
Web Form
AT&T Wireless (now part of Cingular)
[10-digit phone number]@mmode.com
Example: 123456789@mmode.com
Boost Mobile
[10-digit phone number]@myboostmobile.com
Example: 123456789@myboostmobile.com
Web Form
Cingular
[10-digit phone number]@mobile.mycingular.com OR
[10-digit number]@cingularme.com
Example: 1234567890@cingularme.com
Nextel (now part of Sprint Nextel)
[10-digit telephone number]@messaging.nextel.com
Example: 1234567890@messaging.nextel.com
Web Form
Sprint PCS (now Sprint Nextel)
[10-digit phone number]@messaging.sprintpcs.com
Example: 1234567890@messaging.sprintpcs.com
Web Form
T-Mobile
[10-digit phone number]@tmomail.net
Example: 1234567890@tmomail.net
Web Form
Verizon
[10-digit phone number]@vtext.com
Example: 123456789@vtext.com
Web Form
Virgin Mobile USA
[10-digit phone number]@vmobl.com
Example: 1234567890@vmobl.com
Web Form
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