I worked with MX Telecom. Easy, fast, they helped me set up a short code in my country. It's expensive and kind of unnecessarily complicated though. Too many limitations and laws about SMS, at least in my country. Now I use mobile web instead. It's cheap (the same cost as setting up a website), easy to build and maintain, and most cell users are starting to browse the web now, especially since the iPhone came out and web browsing fees dropped. Also, look at it from the user's perspective. Would you rather be getting spam sms messages all the time, or get access to the content you want, when you want it, more anonymously, without being afraid of the sms provider spamming your phone forever after you request any bit of information from them.