http://kly.no/posts/2009_12_08__Varnishstat_for_dummies__.html
Great little article on how to make sense of the varnishstat output.
http://www.strangeloopnetworks.com/
In a similar vein to cloudflare / yottaa, strangeloop offer a performance enhancement service through a physical / cloud based appliance. It uses the standard techniques, js/css combining, sprites, cdn, tailoring to the browser, and so on. No pricing. :-(
http://www.yottaa.com/
Similar to CloudFlare but more expensive ($30/mth no ssl, $130/mth with ssl) it accelerates web sites through the use of CDN, js/css combining, etc.
https://www.cloudflare.com/
loudFlare is an automated CDN / content acceleration type service. It acts as a reverse proxy providing some sort of heuristic security scanning, logging of traffic, and an automatically configured CDN. $15 + $5/site/month.