I am sure some clever programmer can find a way (Chris already showed how to grab category names. There must be a solution for search terms, too)!
The reason this is important to me is because I am using pre-defined search URLs instead of categories. This allows me to have as many sub-categories as I want and file posts under more than one (sub)category. Total freedom! 
At the same time, I would like to gain better rankings in the search engines for my (sub)category pages and the title tag is the most important thing to have your keywords in. So, if I could get my keywords (the actual search phrase) in the title tag, my search engine rankings would improve as a result.
Anybody has an idea?
Miroslav