If you want to flush the DNS cache do:
lookupd -flushcache

Found this interesting thing. It was the Railsday 2005 winner. It is a social commandline for the web. Anybody can create custom commands that achieve something that needs some parameters. Take the command “gim” for example. You can type “gim porsche 911″. The command gim takes a name as parameter and searches for “porsche 911″ pictures. Easy huh? There are allready more than 11 thousand custom commands. And you can create ones yourself. There are also Mac/Linux/Windows frontends for yubnub, firefox extensions and so on.
Yubnub Link