Yahoo is making important improvements to the user interface and the output of its search engine. It will now suggest complete search queries for you as you type. It makes entering queries a lot faster and improves the likelihood that you'll spell your query correctly. Google offers a similar feature in its downloadable add-on, Google Toolbar, but not yet on its Web site.
The suggestions box also shows related search terms. It's pretty smart. When I tried searching for "Corvette," for example, the Search Assist box also displayed "sports cars," "z06," and other related terms.
Other interface improvements include the embedding of video clips in search results pages (some pop up over the page when you play them), as well as photos from Flickr.
Yahoo is also bringing a fair amount of structured data into its search results pages. If you search for a musical artist, you're likely to get a specially-formed result at the top of the page that has links to albums, lyrics, and to music samples that play directly. Movies get a similar treatment. Events are pulled from Yahoo's Upcoming database and displayed in search. Shopping results come in from Yahoo shopping. Sports results, weather, maps, travel, and other data is likewise displayed directly in the search pages, nicely formatted so you can tell what it is.
Yahoo Search's new features are useful. There's likely more to come, too, from Yahoo and its competitors. Most search engines now do more than just parse links and display the content that surrounds them; they instead understand content so they can display information from multiple sites together in useful blocks. Google and Microsoft are already doing this and will no doubt continue to improve how they extract meaning from sites. Ask also has highly-structured search results pages that put the other engines to shame; a good Ask result page is a site to see.
Also coming soon: "Semantic search" engines such as Powerset and Hakia. Their founders say their engines will find what you're looking for even if there's not a single word match between your query and the best result. And their understanding of content should enable the creation of search result pages that answer questions instead of just pointing users at Web sites.