I read about PreviewSeek on techcrunch and they suggested Previewseek help support searchers to apply the right context to their search words. On my review of the service this proved to be limited but having the wiki dictionary link does add pre search education to users.
The most impressive pre search help I have come across has been from our friends at Google. Google labs have the concept of sets and a word predictor e.g. for use on froogle. Become.com also use this technique. Sets are a way for a searcher to express the thoughts in their head when they do not have an exact search word to look for. This is to help identify context I feel and this context can be used to provide better search results.
There is a lot more to value to be provided in the area of pre-search. I predict that the level of service creation in pre search will equal the amount of innovation that has and will continue to be invested in the technology when you press the search button.
I'll highlight what we can expect to see in pre search in a future blog.