'We keep that name moving in the Overhead,' he said, and it seemed to Princess that the wind in the shutter arrays above her blew more forlornly, and the everlasting clicking of the shutters grew more urgent. 'He'd never have wanted to go home. He was a real linesman. His name is in the code, in the wind, in the rigging, and the shutters. Haven't you ever heard the saying "Man's not dead while his name is still spoken"?'
It started here.
The tribute spread to the rest of the World Wide Web in the form of the HTTP header X-Clacks-Overhead: GNU Terry Pratchett. The Clacks Overhead Working Group was formed to make the Clacks header an Internet standard.
Read and contribute to the draft RFC.
Test the Chrome browser extension.
Beyond the HTTP standard, a Clacks tribute can be added to other software. Instructions to do this are being collected at the GNU Terry Pratchett portal.