Yub.js is an extensible client-side web command-line that comes with loads of useful search engines and shortcuts, reusable commands, and lots of other hidden goodies like stopwatches and inline YouTube videos. It also has a flexible API so you can call yub.js commands from anywhere: for example, you can link directly to commands, or access them right from your browser address bar (just set up a single search shortcut pointing at the yub.js API, and get hundreds of other search shortcuts for free).
The whole thing was designed from the outset to be a single page standalone HTML document containing everything needed to work out of the box. It can be installed locally and run right from your computer without the need for a server or web hosting. Since then it has grown considerably and development has been split into separate, more manageable files. The standalone HTML page version is still available, though it is now automatically generated by a ruby script, and comes in minified and source versions. Just save the page directly to your computer or drop it on your server and you're ready to go!
