Lustache - {{Mustache}} templates in Lua
olivinelabs.com
olivinelabs.com
Lua's great for me, as a front-end developer, because it's close enough to Javascript that I can use it as such; and it's close enough to a lot of the languages that we use in the back-end, with the massive benefit of ridiculous speed. Like, seriously fast with Luajit (http://luajit.org/).
We're using Lua for the back-end and middle tier for a browser-based html5 game, and on the front end we use Mustache.js (which provided the basis for lustache) to render a thick-client application. Progressive enhancement at its finest!