Horas and konnichiwa untuk semua

This seems to be very popular SMS gateway
http://www.kannel.org/
Then this can be the system manager for the above SMS gateway (Kannel)
http://ksms.sourceforge.net/

Or, Gnokii is another one
http://www.gnokii.org/
And here is one of the frontends for Gnokii
http://playsms.sourceforge.net/

Some list of other SMS gateways
http://www.developershome.com/sms/freeLibForSMS.asp
(http://www.developershome.com/sms/ is an SMS tutorial)