I handle marketing at Ez Texting. You can check out our new developers center @ <a href="http://www.eztexting.com/developers/" rel="nofollow">http://www.eztexting.com/developers/</a><p>We offer a number of different APIs, and we can definitely handle volume. I can't cite names due to our Privacy Policy, but we're handling some large sites' SMS capabilities through our API (more than a couple ranked top 500 by Quantcast FWIW)<p>If you have any questions, I can answer them for you. Or if you'd like just shoot me an email - josh@eztexting.com