It's hosted at Rackspace Cloud Servers.
See caching plugins review: http://www.tutorial9.net/tutorials/web-tutorials/wordpress-c...
Did your site make it to the front page?
My website made it to #2 on HN front page yesterday : http://news.ycombinator.com/item?id=3521309
I logged about 7k visits with ~200 peak concurrent visits. I wouldn't say that's server-stalling level traffic but the thing is my site is hosted on GitHub Pages so it's entirely static.
I don't mean to troll, I think there's a Wordpress plugin called supercache or something (google wordpress caching) .
But I do want to officially advocate that you rethink whether or not you _really_ need a mysql database, x plugins, and PHP to run a blog
Aside, one quick thing I noticed was that you are using Apache. I would recommend that you switch to nginx. You are already handling your comments with Disqus. I would think that generating static pages and handling comments through Disqus is ideal.
The main thing you need to do is add caching to wordpress (both w3tc and supercache work fine) and if there is still a problem you are probably on the wrong host and should upgrade to either something like linode or a mediatemple grid server or webfaction basic plan.
If you're on a VPS and have caching enabled and still can't manage the traffic I'd say something is wrong with your configuration but just looking at your site I see no caching from either of the plugins I listed.