The main vaCentral site is written on the CakePHP framework. A stripped down version of the Codon framework is used to power the API side of vaCentral. CakePHP and its powerfull ORM features help to quickly write vaCentral.
memcache and APC are both used to cache results and store repeat-use data. Charts and graphs are done using Flot, along with the heavy use of jQuery to spruce up the site.