CLucene is a C++ port of Lucene: the high-performance, full-featured text search engine written in Java. CLucene is faster than lucene as it is written in C++.
Xapian is a Search Engine Library, written in C++ with bindings for Perl, Python, PHP, Java, Tcl, C# and Ruby. Xapian allows you to easily add advanced indexing and search facilities to your applications. See www.xapian.org for more information.