Welcome to the Xapian project website.
Xapian is an Open Source Search Engine Library, released under the GPL. It's written in C++, with bindings to allow use from Perl, Python, PHP, Java, Tcl, C#, Ruby and Lua (so far!)
Xapian is a highly adaptable toolkit which allows developers to easily add advanced indexing and search facilities to their own applications. It supports the Probabilistic Information Retrieval model and also supports a rich set of boolean query operators.
If you're after a packaged search engine for your website, you should take a look at Omega: an application we supply built upon Xapian. Unlike most other website search solutions, Xapian's versatility allows you to extend Omega to meet your needs as they grow.
The latest stable version is 1.2.12, released on 2012-06-27.
The latest 1.0 release is 1.0.23, released on 2011-01-14.
The latest development version is 1.3.0, released on 2012-03-14.