There are two other threads on this subject---an indication of how well the search works <g>. I looked into this a little while ago and basically the way the OpenACS.org site does it is with some hand-crafted .adp/.tcl pairs that get included in the main page.
As has already been suggested, browse through the cvs tree at dev.openacs.org and look at the code for the openacs.org site.
BTW the templates used on the openacs site are (at least the news one, haven't actually worked on the others yet) hardcoded to pull up all the news. I have some mods that allow you to use the template from a subsite and only get the subsite's news. I'm still tinkering with it, but it works fairly well.
Matt