If you've hit an SEO roadblock because of site performance, or if your site is going international, you may want to consider a Content Delivery Network (CDN).
CDN's basically store copies of your website's file data in various places throughout the country (or around the globe!). This way, when a computer far away makes a request for a page on your site, the data does not have to travel from Denver to Shanghai before your user can see the page content. One test case performed here at Denverdata saw a 45% drop in the time it took to load pages in China once the client began using a CDN. Since page load time is such an important performance metric with real conversion impacts, this has a real effect on client engagement and revenue.
Check out this Mashable.com Article for recommendations on the best CDN's on the market today.