I’ve been using www.txtlocal.co.uk for a little while now for sending SMS messages. Their website is very slick and the service works really well.
So far I’ve only used the basic e-mail to SMS but there a comprehensive API so you can integrate sending SMS messages in to your application.
The price is pretty competitive but, for me at least, the most important thing is reliability. I’ve only sent around 75 SMS messages so far but there have been no problems at all, and delivery was very quick.
There are also related services such as – inbound SMS messages, short-code numbers and MMS messages.
Check them out here – www.txtlocal.co.uk