SharePoint Search can be used to power much more than just ad-hoc searches. The standard web parts are highly customizable and there is also the option to create your own that leverage either the Search API or web services.
Search Core Results
I really like that the rendering of the results can be completely customized by updating the XSLT. This provides quite a few opportunities for custom uses without having to recreate all the web part’s plumbing.
By using the “Fixed Keyword Query” option you can pass in static queries. This is especially powerful when interacting with the User Profiles in MOSS. I have been working through some uses with this to provide a dynamic department lists that link to the user profiles. In the past I have seen groups use the regular contact lists, but then owners have to duplicate all of the people’s information that is already stored and maintained in the user’s profile.
Interact with Very Large Lists and Libraries
When working with very large lists and libraries, this can also provide a simpler, more responsive interface making it much easier for users to find what they are looking for.
Spend some time in the sandbox to get a better idea of the available capabilities. I think you will quickly see how they can be applied to your environment and your projects.