You could add a post search filter that removes certain pages depending an a property value or on page type name.
Here I do a reording depending on a boolean property: http://world.episerver.com/Blogs/Per-Nergard/Dates/2013/10/Let-editors-set-pages-to-always-be-on-top-in-search-result-SearchDataSource-not-Find/.
You need to rewrite the filter method to fit your need.
Post on creating filters by Frederik Vig: http://www.frederikvig.com/2009/06/episerver-filter-part-2/
Thank you for the links Per, probably should have mentioned that the site I'm building is MVC based.
Anyhow, support pointed out the ISearchable interface for me and I wrote a short summary on how to use it: http://jonas.kihlsten.se/blog/2013/11/episerver-7search-prevent-content-from-being-indexed/
I have a question regarding search (not Find) in EPiServer 7. I'm wondering how I can prevent a page (or an entire page type) from beeing indexed. I guess I need to do something in the DocumentAdding event but I can't figure out what. Or is there another way to do it?