It costs me 15 cents per message to send or receive. any text message. I hate that!

You can send a text message to a person’s phone using your regular email. It costs the emailer nothing but it will cost the SMS recipient whatever his plan costs. (i.e. it costs me 15 cents)

SMS 411 Blog has the major US providers (below). A reply in the AT&T Forum lists over 100 U.S. and international carriers.

Alltel
[10-digit phone number]@message.alltel.com
Example: 2125551212@message.alltel.com

AT&T (formerly Cingular)
[10-digit phone number]@txt.att.net
Example: 2125551212@txt.att.net

Boost Mobile
[10-digit phone number]@myboostmobile.com
Example: 2125551212@myboostmobile.com

Nextel (now part of Sprint Nextel)
[10-digit telephone number]@messaging.nextel.com
Example: 7035551234@messaging.nextel.com

Sprint PCS (now Sprint Nextel)
[10-digit phone number]@messaging.sprintpcs.com
Example: 2125551234@messaging.sprintpcs.com

T-Mobile
[10-digit phone number]@tmomail.net
Example: 4251234567@tmomail.net

Verizon
[10-digit phone number]@vtext.com
Example: 5552223333@vtext.com

Virgin Mobile USA
[10-digit phone number]@vmobl.com
Example: 5551234567@vmobl.com