Each of these commands will run an ad hoc http server in your current directory. Use this power wisely.

Python 2.x

$ python -m SimpleHTTPServer 8000

Python 3.x

$ python -m http.server 8000

Ruby

Credit: http://barkingiguana.com/2010/04/11/a-one-line-web-server-in-ruby/

$ ruby -rwebrick -e'WEBrick::HTTPServer.new(:Port => 8000, :DocumentRoot => Dir.pwd).start'

Perl

Credit: http://www.perlmonks.org/?node_id=865239

$ perl -MCPAN -e "install HTTP::Server::Brick"   # install dependency
$ perl -MHTTP::Server::Brick -e '$s=HTTP::Server::Brick->new(port=>8000); $s->mount("/"=>{path=>"."}); $s->start'

Node.js #1

$ npm install -g http-server   # install dependency
$ http-server -p 8000

Node.js #2

# Runs in Node.js using node-static. No directory listings.
$ npm install -g node-static   # install dependency
$ static -p 8000