Many people have now seen the website LetMeGoogleThatForYou.com. This is an entertaining example that points to what usability in searching means. Our discussion led to thinking of natural-language question-answer search services, which have seen popularity at different points. My personal favorite is ChaCha, which allows queries sent and returned over SMS, which can be very useful from time to time.
We also discussed what Jason Kottke has termed single-serving sites. These websites are, in theory, the pinnacle of usable. They have one function for which they are extremely easy and effective and efficient. And entertaining.