i used to work with
www.clickatell.com its higher volume demand, so you might not get a account. But if you do, they have lots of api's to connect with it. Perl, Php, Cgi, Http, Mail, etc.. and if you only use it for a sms now and then, the price aint that bad either but i -always- got my sms in. It also gives you feedback if you create a callback.php or something on your server, then it contacts that url with certain options so you can verify if the sms made it or not. With smsd under linux, it also gives you feedback if the sms made it or not (but in this case if everything was still working, connection between the phone, contacting sms nr of operator etc)
// Erik (binkey.nl)