Yes.
The easiest way is to use the [man]mail[/man] function sending the email to the phone number's carrier.
i.e.
5555551212@cingularme.com would sent the SMS to 555-555-1212, a cingular user.
Most carriers have this ability but you have to address the email's to the right place. i.e. cingularme.com, vtext.com, etc...
