http://mightytext.net/
I find texting to be a time-consuming and laborious endeavor. But it appears to be the preferred form of communication among the younger set, and I've lately found myself in long text conversations with some lady friends.
I found MightyText last night, installed it today and already love it. It syncs my contact list and my existing threads with my Android phone, and I used a browser window to carry on a conversation today, typing out my messages much more quickly than I could have on my phone's keyboard.
I downloaded the app at the Apps Store, then went to the website and registered it with the Gmail address that my phone uses. The sync was automatic. I was ready to go in a minute.
It may not be for everyone. But I've already had one provider say "Wow!" and ask for the URL, so I thought I'd post it here.