Although the Out of the Box People Search is quite nice, most clients would want to extend the people search with their own custom search options.
Fortunately, as with the adding of properties to the Advanced Search Box, this is fairly straightforward to achieve. The following article http://www.sharepointblogs.com/aaronrh/archive/2007/05/21/adding-additional-properties-to-the-moss-people-search.aspx explains how to do this.
Essentially the most important step is adding the following to the properties in the People Search WebPart:
<property name="NewProp" managedname="NewProp" profileuri="urn:schemas-microsoft-com:sharepoint:portal:profile:NewProp">
