Google has written a blog post and put together a video about one of the biggest new features that comes with the Android 1.6 update (better known as "Donut") - the Quick Search Box. This is a system-wide search engine for your device, meaning that it can look through apps, contacts, and browser history as well as content from the Web.
It'll also provide suggestions as you type, meaning that you won't need to muck about with an on-screen keyboard as much as you might with a traditional search box. Quick Search Box will also learn from your habits and give you faster access to things you search for the most often.
You can also use voice on the search box - tapping the microphone icon and speaking your query or the name of the person you want to call. That only works in English for now, though. Lastly, developers will be pleased to hear that they can hook into the Quick Search Box too - Google's provided some tips on that front on its developer blog.