Send free SMS from your computer or a smart phone and receive replies by email. (myintimcity.com)
There's all sorts of free SMS services out in the wild but this one is unique because you can use your current phone number and not use a random generic one. (pocketberry.com)
There are also free SMS services available, which are often sponsored and allow sending SMS from a PC connected to the internet. (petesgrillandpizza.com)