I'll just throw in front end libraries too. We weren't able to leverage HTML5 due to our market segment.

Internal: Git, GitHub, Basecamp

Client: HTML-not-quite-5, jQuery, Lodash, Fine Uploader, Select2, Redactor, Fancybox 2, Sass/Compass

Server: Apache 2.2, MySQL 5.1, PHP 5.3, Laravel 3, PHPMailer

Hosting: MediaTemple DV 4.0 (CentOS 5.8)