Especially in the Development industry, SMS is very big at the moment. It is a great tool to reach the billions of people who are not in the Internet yet.
This is a small list of projects that do SMS interaction (with a lot of people)
- www.myelva.com/
- www.ushahidi.com (and www.crowdmap.com )
- http://textit.in
- www.rapidsms.org/ (powers textit and www.ureport.ug )
- http://www.votomobile.org (includes voice)
This is a big market.