Every so often our cable internet (Time Warner Road Runner) will go "out." Only it's not really "out": the cable modem's internet connection is still on and I can ping IP addresses. What's really happening is Road Runner's DNS servers stop responding to DNS queries. This doesn't happen very often, and it is usually resolved in a few minutes, but that's too long when I'm trying to work.

The solution: OpenDNS. These guys run a top-notch DNS service. It's free, reliable, fast, and supposedly safer. The Getting Started page has detailed instructions for using OpenDNS's servers in place of your ISP's servers.