Swish-e, a free open-source Unix search engine, Swish-e is fast at indexing and searching, and quite flexible. It can handle simple authentication, indexes HTML, text, XML, and (via converters), PDF, MS Word, Excel and MP3 ID3 tags, with an emphasis on storing feilds/tags for specifying during search. Resuts can be sorted by relevance, date, size, and other fields. It runs as a CGI to a web server (Apache recommended), and has a fairly active user and developer base. New features include adjustments to the relevance algorithm, "near" operator and "?" single character wildcard operator (in addition to "*").