Open Public Access Catalogs (OPACs) provide patrons with a user interface (UI) to help their information seeking tasks. Even though many OPAC UIs are now web-based, their architectures are often static, which does not allow them to integrate user assistance modules dynamically. We report on a UI that supports integration of such modules, while providing a usable and rich environment. We explore how Asynchronous JavaScript + XML (AJAX) can be employed to create an OPAC UI that offers a better user experience and task support. Our developed UI features a modular architecture that combines several Natural Language Processing (NLP) modules employed to enhance information seeking. Our UI manages queries in a novel way with a tabbed interface featuring an overview/details presentation model, and an AJAX query results data grid. Preliminary user testing results are also presented.