This document discusses building intelligent applications using various open source tools such as Apache Lucene, Mahout, OpenNLP, and others. It defines intelligent applications as those that learn from past behavior and data to adapt and provide personalized insights. Examples of intelligent applications mentioned include Netflix and Amazon. The document then provides an overview of various tools that can be used as building blocks for different components of intelligent applications, such as acquisition, language analysis, search, organization, and user modeling. It also gives examples of how to tie these tools together in an intelligent application and provides resources for further information.