Free API for Search the Web instead of Google Search API

Entireweb: http://entireweb.com/services/
Quora: http://www.quora.com/What-can-I-do-with-Blekkos-API
...

True Knowledge - The Internet Answer Engine

http://www.trueknowledge.com/

Just a beta version but very impressive about what it can do for us.

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Cheers,
Vu

Open source search engine

The below is some collected information relevant to up-to-date open source search engine toolkits:

1) Lucene: http://lucene.apache.org/ (Java)
--> CLucene: http://sourceforge.net/projects/clucene/ (C++)

2) Minion: https://minion.dev.java.net
3) Galago: http://www.galagosearch.org/

4) Xapian: http://xapian.org/ (C++)

5) http://www.searchenginecaffe.com/2007/03/open-source-search-engines-in-java-and.html (very informative)

6) Minion vs. Lucene: http://blogs.sun.com/searchguy/entry/minion_and_lucene_query_languages

7) Search Engine Wrapper (Yee Fan Tan - NUS): http://wing.comp.nus.edu.sg/~tanyeefa/downloads/searchenginewrapper/

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Cheers,
Vu