- Check out DNS Prefetching SPDY - http://en.wikipedia.org/wiki/SPDY
- Update the .manifest version upon build
Caching can be done on many levels, choose the correct level for each requirement.
I.E. We can cache the entire front page completely, server all HTML from a CDN such as Cloudfront. Only action is Search of this.
One cool trick is you can point 10 CNames at Cloudfront, i.e. images1.site.com, images2.site.com, etc, and then in your application code when you generate a link to an image you can dynamically change the domain part of the url to the ones you configured in your DNS to point at cloudfront, and that allows for the up to 10 simultaneous connections browsers can have while downloading content. So rather than happening sequentially, the browser can download all at the same time.
APC provides an admin interface at the root of the project.
Slim has HTTP caching support with etag,last modified and expires methods