Our new term extraction service analyzes text and an optional query, returning a list of the key concepts from the text. You can use the service for a variety of different purposes. For example, Y!Q uses it to determine key concepts within the search context and then uses those terms for augmenting a user's search query.
U. Riss, and O. Grebner. Proceedings of I-KNOW '06, 6th International Conference on Knowledge Management, Graz, Austria, September 6 - 8, 2006, (September 2006)