Here is a SMS tool that I used a lot while working abroad in areas with little to no Internet access.

http://www.frontlinesms.com

At the time, I just had the desktop application, but since then, I see that they've hosted a solution online for $10/mo.

What makes it cool (at least the online version) is that you could build autoreplies into the interface, so when people txt with certain messages, you could automatically respond with canned responses.

Indeed, Fronline SMS has been brought up quite a few times before on the TechSoup forum:

text messages helps combat human trafficking

Sending text messages to 50 non-smart phones

Shouldn’t the Word Phone Be Removed from Mobile? The Use of the Mobile by Nonprofits for Development

Lessons From Haiti: Uses of New Media in Disaster Recovery Efforts

Anything new to say about it?