Lucene is a popular, open-source search engine that's freely available for anyone to download and use. Lucene is a basic platform, and because it's written in Java it's highly extensible and can be adapted to many purposes.
If you're a proficient programmer, or simply are curious about what the code looks like for a world-class search engine, check out today's SearchDay article, How to Hack Your Own Search Engine, which is a review of a new book, Lucene in Action. The book offers detailed instructions for downloading and customizing Lucene yourself, and the companion site also makes all of the source code examples available for your perusal.
Optimising Digital Marketing Campaigns with Search, Social and Analytics
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