Short answer: it depends.
Longer answer: If you are not in the US, then you can ask your telephone carrier if they support this, and how to activate it. BT for example does. Usually you need to either be using VoIP or a T1 with a dedicated data channel, but different telcos have different ways of doing this.
If you are in the US, things get much harder. There is no easy way for a end-user to do this. If you were American Idol and wanted to SMS enable some lines to receive votes, the cell carriers would be happy to help. As you will be generating LOTS of SMS which means LOTS of revenue. But Joe Smith, with no promise of big money will not get that kind of service. I’ve heard that $250,000 will buy you a connection to a carrier’s SMSC, but I cannot confirm this.
One possible solution, checkout Synaverse, www.synaverse.com They have a product called SMS-IP that seems to be able to SMS-enable landlines. Catch is, they have to be THEIR land lines, maybe you could buy a DID from them, and have them handle the SMS, while you handle the voice. Haven’t tried it.
Hope that helps.