AIDA/Web is a Smalltalk web application framework for building complex web applications with integrated Ajax support, rich collection of web components to build web pages programatically, MVC-like separation of presentation from domain, REST-like nice looking and bookmarkable url links, with integrated session and security management, a Swazoo web server and many more.
AIDA/Web is known by its simplicity but still allows building most demanding web applications of many sorts. It has everything you need for a real web app, together with Ajax (which is not additional but integral part of Aida).
It is also a mature one, running web apps in production since 1996. It is used in many intranet business apps from Gas billing system for all gas in Slovenia to logistics management system called e-logis and recently a CMS like system for Quality and Business process management.