Not exactly what you're asking for but I use Google Voice from this. I don't even have to have my phone with my or load anything on the PC. Any internet-connect PC can be used.
There are more that just do SMS like those, but SMS2PC and one of the notification versions ( https://market.android.com/details?id=org.damazio.notifier&feature=search_result ) were the only ones I tried. I actually have a both the notification and SMS2PC installed on my laptop, as I liked the notification better with the notifier but you can't reply.
There are a few like https://market.android.com/details?id=com.fjsoft.myphoneexplorer.client which does a bit of everything. I have had it installed for a bit but never used it in this way. I let it run to see what happens when a text or phone call comes in, and today I am apparently not popular enough to get a phone call or text message (I started it up as I started typing this)
Or as mentioned above Google Voice also allows you to text from your PC, your phone isn't even necessary in this instance.