Database systems have been driving dynamic web sites since the early 90s, and caching and materialization have been the major techniques to improve the performance, scalability, and manageability of such web databases. Different from a traditional database environment, the software components of a web database, including web servers, database servers, application servers, and possibly additional middleware, are largely independent from one another, even though they work together as a holistic system. Caching and materialization techniques for such web databases consider a number of issues at different parts of the system and they bring interesting challenges and opportunities. Caching and Materialization for Web Databases adopts a data management point of view to describe the system architectures of web databases, and analyze the research issues related to caching and materialization in such architectures. It also presents the state of the art in caching and materialization for web databases and organizes current approaches according to the fundamental questions, namely how to store, how to use, and how to maintain cached/materialized web data. Finally, it associates work in caching and materialization for web databases to similar techniques in other related areas, such as data warehousing, distributed systems, and distributed databases.