SharePoint 2007: Advanced Search Customisations (Link Dump)

These articles all say more or less the same thing, however some may be missing some steps, or may offer more details than others.
Note that although most of articles mention MOSS, I've found that this works with Windows SharePoint Services 3.0 too.

Ishai from SPSTips: How to Add Properties to advanced search in MOSS 2007
http://www.sharepoint-tips.com/2006/07/found-it-how-to-add-properties-to.html

Adding Property Restrictions
http://www.jjfblog.com/2007/01/searching-custom-column-values-in-moss.html

MOSS Search Article
Interesting piece of information in this article:

For new column, you should select the column name without "ows_" prefix.
But for existing/built-in SharePoint column, you can select the column name with "ows_" prefix. Every built-in SharePoint colum has a crawled property and has the "ows_" prefix.

http://www.mosssearch.com/searchcolumn.html

Advanced Search on your own metadata
http://www.sharepointblogs.com/andymay/archive/2006/11/09/15913.aspx

Fixed Keyword Queries in your Search
http://www.u2u.info/Blogs/Patrick/Lists/Posts/Post.aspx?ID=1668

and then customize the way the search results are displayed
http://www.u2u.info/Blogs/Patrick/Lists/Posts/Post.aspx?ID=1669

If you have captured certain meta data which you would like to show in your search results this is the way to do it:
How to: Change the Properties Returned in the Core Search Results