File-storage, forums, survey, news, edit-this-page, all have search service contracts. Probably other packages I haven't thought of off the top of my head.
Here is the tsearch2 install doc
http://cvs.openacs.org/cvs/*checkout*/openacs-4/packages/acs-core-docs/www/install-full-text-search-tsearch2.html?rev=1.2.2.5
I am surpised you can't find this in your install. This was tagged to be included in openacs-5-2-final.
