I have not used Lua for web apps, but I do know that the Kepler project is quite active these days. They're developing a whole suite of tools for a Lua web stack. www.keplerproject.org
Personally I love Lua as a language. It has just the right blend of functional, imperative, and OO concepts to let me dabble in different styles as I see fit. It's an elegant language which also has a great community.
Lua is what I turn to when I want to prototype an idea or just scratch out a rough draft of some calculations. I have yet to write any in-the-large software in it, but I suspect that it would scale nicely as well.
I've looked at Lua in the past. I chose not to spend time learning it because it doesn't seem to offer anything. It's basically Python with a smaller footprint and fewer libraries, as far I can tell.
The small footprint seems to be the most touted feature. I'm sure it's useful if you need it, but if not, I don't see the point.
i had the same reaction (lua resembling python but with a focus on small footprint and a much smaller standard library.)
having "batteries included"/mature web frameworks often trumps the innate benefits of the language, i.e. other people who have spent thousands of hours on mostly boring glue -- ORMs, unicode support, templating engines, caching, getting around browser quirks -- to enable you to focus on your app.
furthermore, you're generally going to be bounded by IO/the database or RAM or some other factor in which case the speed of the language is mostly irrelevant.
it's certainly possible to do web development in any language, but why bother swimming upstream when python/php/ruby do a lot of the hard work for you? it's hard enough just to write your application without having to write the infrastructure beneath it too.
The other way to look at it is that Lua has a simple enough binding interface that it's like a "high-level layer on top of C." So you can write C, or write Lua, and slop things around between them as necessary, run multiple interpreters, whatever you feel like.
Python is more focused on extending the language as a singular entity, and (not having actually written extensions) it seems to have more strenuous requirements.
Right now I'm focused on haXe, though, cause with that language, you get several platform options, including a Lua-like interpreter(Neko).
I know a couple of success cases in Brazil: http://www.vale.com (among the 5 biggest Metal & Mining companies in the world) and http://www.petrobras.com/ (among the 10 biggest oil & gas companies in the world) use Lua for some parts of their web site.
Personally I love Lua as a language. It has just the right blend of functional, imperative, and OO concepts to let me dabble in different styles as I see fit. It's an elegant language which also has a great community.
Lua is what I turn to when I want to prototype an idea or just scratch out a rough draft of some calculations. I have yet to write any in-the-large software in it, but I suspect that it would scale nicely as well.
Anyway, have fun with Lua. I know I am!