Instant Domain Search
I attended Y Combinator’s first Startup School in 2005, and left inspired to stop doing hourly consulting work and start building products. I spent hours that evening searching for available domain names for products I wanted to make. The user experience was terrible. WHOIS queries often took seconds to run, and I had to jump from one service to another to avoid rate the limits designed to stop spambots from harvesting email addresses.
That night, I realized that you could do a very fast DNS query to see if a domain name was in use. A few hours later, I and launched the service to friends and other Startup School attendees. TechCrunch reported on it a few days later, and many clones have launched since.
I operate Instant Domain Search in my spare time, and I focus on making it fast. The site determines which of several globally distributed search servers can answer your queries fastest, all to deliver the fastest domain name search in the world.